feat: migrate from Cedar to SpiceDB authorization system

This is a major architectural change that replaces the Cedar policy-based
authorization system with SpiceDB's relation-based authorization.

Key changes:

- Migrate from Rust to Go implementation
- Replace Cedar policies with SpiceDB schema and relationships
- Switch from envoy `ext_authz` with Cedar to SpiceDB permission checks
- Update build system and dependencies for Go ecosystem
- Maintain Envoy integration for external authorization

This change enables more flexible permission modeling through SpiceDB's
Google Zanzibar inspired relation-based system, supporting complex
hierarchical permissions that were difficult to express in Cedar.

Breaking change: Existing Cedar policies and Rust-based configuration
will no longer work and need to be migrated to SpiceDB schema.

1 files changed, 0 insertions, 612 deletions

diff --git a/vendor/itertools/src/grouping_map.rs b/vendor/itertools/src/grouping_map.rs
deleted file mode 100644
index 86cb55dc..00000000
--- a/vendor/itertools/src/grouping_map.rs
+++ /dev/null
@@ -1,612 +0,0 @@
-use crate::{
-    adaptors::map::{MapSpecialCase, MapSpecialCaseFn},
-    MinMaxResult,
-};
-use std::cmp::Ordering;
-use std::collections::HashMap;
-use std::hash::Hash;
-use std::iter::Iterator;
-use std::ops::{Add, Mul};
-
-/// A wrapper to allow for an easy [`into_grouping_map_by`](crate::Itertools::into_grouping_map_by)
-pub type MapForGrouping<I, F> = MapSpecialCase<I, GroupingMapFn<F>>;
-
-#[derive(Clone)]
-pub struct GroupingMapFn<F>(F);
-
-impl<F> std::fmt::Debug for GroupingMapFn<F> {
-    debug_fmt_fields!(GroupingMapFn,);
-}
-
-impl<V, K, F: FnMut(&V) -> K> MapSpecialCaseFn<V> for GroupingMapFn<F> {
-    type Out = (K, V);
-    fn call(&mut self, v: V) -> Self::Out {
-        ((self.0)(&v), v)
-    }
-}
-
-pub(crate) fn new_map_for_grouping<K, I: Iterator, F: FnMut(&I::Item) -> K>(
-    iter: I,
-    key_mapper: F,
-) -> MapForGrouping<I, F> {
-    MapSpecialCase {
-        iter,
-        f: GroupingMapFn(key_mapper),
-    }
-}
-
-/// Creates a new `GroupingMap` from `iter`
-pub fn new<I, K, V>(iter: I) -> GroupingMap<I>
-where
-    I: Iterator<Item = (K, V)>,
-    K: Hash + Eq,
-{
-    GroupingMap { iter }
-}
-
-/// `GroupingMapBy` is an intermediate struct for efficient group-and-fold operations.
-///
-/// See [`GroupingMap`] for more informations.
-pub type GroupingMapBy<I, F> = GroupingMap<MapForGrouping<I, F>>;
-
-/// `GroupingMap` is an intermediate struct for efficient group-and-fold operations.
-/// It groups elements by their key and at the same time fold each group
-/// using some aggregating operation.
-///
-/// No method on this struct performs temporary allocations.
-#[derive(Clone, Debug)]
-#[must_use = "GroupingMap is lazy and do nothing unless consumed"]
-pub struct GroupingMap<I> {
-    iter: I,
-}
-
-impl<I, K, V> GroupingMap<I>
-where
-    I: Iterator<Item = (K, V)>,
-    K: Hash + Eq,
-{
-    /// This is the generic way to perform any operation on a `GroupingMap`.
-    /// It's suggested to use this method only to implement custom operations
-    /// when the already provided ones are not enough.
-    ///
-    /// Groups elements from the `GroupingMap` source by key and applies `operation` to the elements
-    /// of each group sequentially, passing the previously accumulated value, a reference to the key
-    /// and the current element as arguments, and stores the results in an `HashMap`.
-    ///
-    /// The `operation` function is invoked on each element with the following parameters:
-    ///  - the current value of the accumulator of the group if there is currently one;
-    ///  - a reference to the key of the group this element belongs to;
-    ///  - the element from the source being aggregated;
-    ///
-    /// If `operation` returns `Some(element)` then the accumulator is updated with `element`,
-    /// otherwise the previous accumulation is discarded.
-    ///
-    /// Return a `HashMap` associating the key of each group with the result of aggregation of
-    /// that group's elements. If the aggregation of the last element of a group discards the
-    /// accumulator then there won't be an entry associated to that group's key.
-    ///
-    /// ```
-    /// use itertools::Itertools;
-    ///
-    /// let data = vec![2, 8, 5, 7, 9, 0, 4, 10];
-    /// let lookup = data.into_iter()
-    ///     .into_grouping_map_by(|&n| n % 4)
-    ///     .aggregate(|acc, _key, val| {
-    ///         if val == 0 || val == 10 {
-    ///             None
-    ///         } else {
-    ///             Some(acc.unwrap_or(0) + val)
-    ///         }
-    ///     });
-    ///
-    /// assert_eq!(lookup[&0], 4);        // 0 resets the accumulator so only 4 is summed
-    /// assert_eq!(lookup[&1], 5 + 9);
-    /// assert_eq!(lookup.get(&2), None); // 10 resets the accumulator and nothing is summed afterward
-    /// assert_eq!(lookup[&3], 7);
-    /// assert_eq!(lookup.len(), 3);      // The final keys are only 0, 1 and 2
-    /// ```
-    pub fn aggregate<FO, R>(self, mut operation: FO) -> HashMap<K, R>
-    where
-        FO: FnMut(Option<R>, &K, V) -> Option<R>,
-    {
-        let mut destination_map = HashMap::new();
-
-        self.iter.for_each(|(key, val)| {
-            let acc = destination_map.remove(&key);
-            if let Some(op_res) = operation(acc, &key, val) {
-                destination_map.insert(key, op_res);
-            }
-        });
-
-        destination_map
-    }
-
-    /// Groups elements from the `GroupingMap` source by key and applies `operation` to the elements
-    /// of each group sequentially, passing the previously accumulated value, a reference to the key
-    /// and the current element as arguments, and stores the results in a new map.
-    ///
-    /// `init` is called to obtain the initial value of each accumulator.
-    ///
-    /// `operation` is a function that is invoked on each element with the following parameters:
-    ///  - the current value of the accumulator of the group;
-    ///  - a reference to the key of the group this element belongs to;
-    ///  - the element from the source being accumulated.
-    ///
-    /// Return a `HashMap` associating the key of each group with the result of folding that group's elements.
-    ///
-    /// ```
-    /// use itertools::Itertools;
-    ///
-    /// #[derive(Debug, Default)]
-    /// struct Accumulator {
-    ///   acc: usize,
-    /// }
-    ///
-    /// let lookup = (1..=7)
-    ///     .into_grouping_map_by(|&n| n % 3)
-    ///     .fold_with(|_key, _val| Default::default(), |Accumulator { acc }, _key, val| {
-    ///         let acc = acc + val;
-    ///         Accumulator { acc }
-    ///      });
-    ///
-    /// assert_eq!(lookup[&0].acc, 3 + 6);
-    /// assert_eq!(lookup[&1].acc, 1 + 4 + 7);
-    /// assert_eq!(lookup[&2].acc, 2 + 5);
-    /// assert_eq!(lookup.len(), 3);
-    /// ```
-    pub fn fold_with<FI, FO, R>(self, mut init: FI, mut operation: FO) -> HashMap<K, R>
-    where
-        FI: FnMut(&K, &V) -> R,
-        FO: FnMut(R, &K, V) -> R,
-    {
-        self.aggregate(|acc, key, val| {
-            let acc = acc.unwrap_or_else(|| init(key, &val));
-            Some(operation(acc, key, val))
-        })
-    }
-
-    /// Groups elements from the `GroupingMap` source by key and applies `operation` to the elements
-    /// of each group sequentially, passing the previously accumulated value, a reference to the key
-    /// and the current element as arguments, and stores the results in a new map.
-    ///
-    /// `init` is the value from which will be cloned the initial value of each accumulator.
-    ///
-    /// `operation` is a function that is invoked on each element with the following parameters:
-    ///  - the current value of the accumulator of the group;
-    ///  - a reference to the key of the group this element belongs to;
-    ///  - the element from the source being accumulated.
-    ///
-    /// Return a `HashMap` associating the key of each group with the result of folding that group's elements.
-    ///
-    /// ```
-    /// use itertools::Itertools;
-    ///
-    /// let lookup = (1..=7)
-    ///     .into_grouping_map_by(|&n| n % 3)
-    ///     .fold(0, |acc, _key, val| acc + val);
-    ///
-    /// assert_eq!(lookup[&0], 3 + 6);
-    /// assert_eq!(lookup[&1], 1 + 4 + 7);
-    /// assert_eq!(lookup[&2], 2 + 5);
-    /// assert_eq!(lookup.len(), 3);
-    /// ```
-    pub fn fold<FO, R>(self, init: R, operation: FO) -> HashMap<K, R>
-    where
-        R: Clone,
-        FO: FnMut(R, &K, V) -> R,
-    {
-        self.fold_with(|_, _| init.clone(), operation)
-    }
-
-    /// Groups elements from the `GroupingMap` source by key and applies `operation` to the elements
-    /// of each group sequentially, passing the previously accumulated value, a reference to the key
-    /// and the current element as arguments, and stores the results in a new map.
-    ///
-    /// This is similar to [`fold`] but the initial value of the accumulator is the first element of the group.
-    ///
-    /// `operation` is a function that is invoked on each element with the following parameters:
-    ///  - the current value of the accumulator of the group;
-    ///  - a reference to the key of the group this element belongs to;
-    ///  - the element from the source being accumulated.
-    ///
-    /// Return a `HashMap` associating the key of each group with the result of folding that group's elements.
-    ///
-    /// [`fold`]: GroupingMap::fold
-    ///
-    /// ```
-    /// use itertools::Itertools;
-    ///
-    /// let lookup = (1..=7)
-    ///     .into_grouping_map_by(|&n| n % 3)
-    ///     .reduce(|acc, _key, val| acc + val);
-    ///
-    /// assert_eq!(lookup[&0], 3 + 6);
-    /// assert_eq!(lookup[&1], 1 + 4 + 7);
-    /// assert_eq!(lookup[&2], 2 + 5);
-    /// assert_eq!(lookup.len(), 3);
-    /// ```
-    pub fn reduce<FO>(self, mut operation: FO) -> HashMap<K, V>
-    where
-        FO: FnMut(V, &K, V) -> V,
-    {
-        self.aggregate(|acc, key, val| {
-            Some(match acc {
-                Some(acc) => operation(acc, key, val),
-                None => val,
-            })
-        })
-    }
-
-    /// See [`.reduce()`](GroupingMap::reduce).
-    #[deprecated(note = "Use .reduce() instead", since = "0.13.0")]
-    pub fn fold_first<FO>(self, operation: FO) -> HashMap<K, V>
-    where
-        FO: FnMut(V, &K, V) -> V,
-    {
-        self.reduce(operation)
-    }
-
-    /// Groups elements from the `GroupingMap` source by key and collects the elements of each group in
-    /// an instance of `C`. The iteration order is preserved when inserting elements.
-    ///
-    /// Return a `HashMap` associating the key of each group with the collection containing that group's elements.
-    ///
-    /// ```
-    /// use itertools::Itertools;
-    /// use std::collections::HashSet;
-    ///
-    /// let lookup = vec![0, 1, 2, 3, 4, 5, 6, 2, 3, 6].into_iter()
-    ///     .into_grouping_map_by(|&n| n % 3)
-    ///     .collect::<HashSet<_>>();
-    ///
-    /// assert_eq!(lookup[&0], vec![0, 3, 6].into_iter().collect::<HashSet<_>>());
-    /// assert_eq!(lookup[&1], vec![1, 4].into_iter().collect::<HashSet<_>>());
-    /// assert_eq!(lookup[&2], vec![2, 5].into_iter().collect::<HashSet<_>>());
-    /// assert_eq!(lookup.len(), 3);
-    /// ```
-    pub fn collect<C>(self) -> HashMap<K, C>
-    where
-        C: Default + Extend<V>,
-    {
-        let mut destination_map = HashMap::new();
-
-        self.iter.for_each(|(key, val)| {
-            destination_map
-                .entry(key)
-                .or_insert_with(C::default)
-                .extend(Some(val));
-        });
-
-        destination_map
-    }
-
-    /// Groups elements from the `GroupingMap` source by key and finds the maximum of each group.
-    ///
-    /// If several elements are equally maximum, the last element is picked.
-    ///
-    /// Returns a `HashMap` associating the key of each group with the maximum of that group's elements.
-    ///
-    /// ```
-    /// use itertools::Itertools;
-    ///
-    /// let lookup = vec![1, 3, 4, 5, 7, 8, 9, 12].into_iter()
-    ///     .into_grouping_map_by(|&n| n % 3)
-    ///     .max();
-    ///
-    /// assert_eq!(lookup[&0], 12);
-    /// assert_eq!(lookup[&1], 7);
-    /// assert_eq!(lookup[&2], 8);
-    /// assert_eq!(lookup.len(), 3);
-    /// ```
-    pub fn max(self) -> HashMap<K, V>
-    where
-        V: Ord,
-    {
-        self.max_by(|_, v1, v2| V::cmp(v1, v2))
-    }
-
-    /// Groups elements from the `GroupingMap` source by key and finds the maximum of each group
-    /// with respect to the specified comparison function.
-    ///
-    /// If several elements are equally maximum, the last element is picked.
-    ///
-    /// Returns a `HashMap` associating the key of each group with the maximum of that group's elements.
-    ///
-    /// ```
-    /// use itertools::Itertools;
-    ///
-    /// let lookup = vec![1, 3, 4, 5, 7, 8, 9, 12].into_iter()
-    ///     .into_grouping_map_by(|&n| n % 3)
-    ///     .max_by(|_key, x, y| y.cmp(x));
-    ///
-    /// assert_eq!(lookup[&0], 3);
-    /// assert_eq!(lookup[&1], 1);
-    /// assert_eq!(lookup[&2], 5);
-    /// assert_eq!(lookup.len(), 3);
-    /// ```
-    pub fn max_by<F>(self, mut compare: F) -> HashMap<K, V>
-    where
-        F: FnMut(&K, &V, &V) -> Ordering,
-    {
-        self.reduce(|acc, key, val| match compare(key, &acc, &val) {
-            Ordering::Less | Ordering::Equal => val,
-            Ordering::Greater => acc,
-        })
-    }
-
-    /// Groups elements from the `GroupingMap` source by key and finds the element of each group
-    /// that gives the maximum from the specified function.
-    ///
-    /// If several elements are equally maximum, the last element is picked.
-    ///
-    /// Returns a `HashMap` associating the key of each group with the maximum of that group's elements.
-    ///
-    /// ```
-    /// use itertools::Itertools;
-    ///
-    /// let lookup = vec![1, 3, 4, 5, 7, 8, 9, 12].into_iter()
-    ///     .into_grouping_map_by(|&n| n % 3)
-    ///     .max_by_key(|_key, &val| val % 4);
-    ///
-    /// assert_eq!(lookup[&0], 3);
-    /// assert_eq!(lookup[&1], 7);
-    /// assert_eq!(lookup[&2], 5);
-    /// assert_eq!(lookup.len(), 3);
-    /// ```
-    pub fn max_by_key<F, CK>(self, mut f: F) -> HashMap<K, V>
-    where
-        F: FnMut(&K, &V) -> CK,
-        CK: Ord,
-    {
-        self.max_by(|key, v1, v2| f(key, v1).cmp(&f(key, v2)))
-    }
-
-    /// Groups elements from the `GroupingMap` source by key and finds the minimum of each group.
-    ///
-    /// If several elements are equally minimum, the first element is picked.
-    ///
-    /// Returns a `HashMap` associating the key of each group with the minimum of that group's elements.
-    ///
-    /// ```
-    /// use itertools::Itertools;
-    ///
-    /// let lookup = vec![1, 3, 4, 5, 7, 8, 9, 12].into_iter()
-    ///     .into_grouping_map_by(|&n| n % 3)
-    ///     .min();
-    ///
-    /// assert_eq!(lookup[&0], 3);
-    /// assert_eq!(lookup[&1], 1);
-    /// assert_eq!(lookup[&2], 5);
-    /// assert_eq!(lookup.len(), 3);
-    /// ```
-    pub fn min(self) -> HashMap<K, V>
-    where
-        V: Ord,
-    {
-        self.min_by(|_, v1, v2| V::cmp(v1, v2))
-    }
-
-    /// Groups elements from the `GroupingMap` source by key and finds the minimum of each group
-    /// with respect to the specified comparison function.
-    ///
-    /// If several elements are equally minimum, the first element is picked.
-    ///
-    /// Returns a `HashMap` associating the key of each group with the minimum of that group's elements.
-    ///
-    /// ```
-    /// use itertools::Itertools;
-    ///
-    /// let lookup = vec![1, 3, 4, 5, 7, 8, 9, 12].into_iter()
-    ///     .into_grouping_map_by(|&n| n % 3)
-    ///     .min_by(|_key, x, y| y.cmp(x));
-    ///
-    /// assert_eq!(lookup[&0], 12);
-    /// assert_eq!(lookup[&1], 7);
-    /// assert_eq!(lookup[&2], 8);
-    /// assert_eq!(lookup.len(), 3);
-    /// ```
-    pub fn min_by<F>(self, mut compare: F) -> HashMap<K, V>
-    where
-        F: FnMut(&K, &V, &V) -> Ordering,
-    {
-        self.reduce(|acc, key, val| match compare(key, &acc, &val) {
-            Ordering::Less | Ordering::Equal => acc,
-            Ordering::Greater => val,
-        })
-    }
-
-    /// Groups elements from the `GroupingMap` source by key and finds the element of each group
-    /// that gives the minimum from the specified function.
-    ///
-    /// If several elements are equally minimum, the first element is picked.
-    ///
-    /// Returns a `HashMap` associating the key of each group with the minimum of that group's elements.
-    ///
-    /// ```
-    /// use itertools::Itertools;
-    ///
-    /// let lookup = vec![1, 3, 4, 5, 7, 8, 9, 12].into_iter()
-    ///     .into_grouping_map_by(|&n| n % 3)
-    ///     .min_by_key(|_key, &val| val % 4);
-    ///
-    /// assert_eq!(lookup[&0], 12);
-    /// assert_eq!(lookup[&1], 4);
-    /// assert_eq!(lookup[&2], 8);
-    /// assert_eq!(lookup.len(), 3);
-    /// ```
-    pub fn min_by_key<F, CK>(self, mut f: F) -> HashMap<K, V>
-    where
-        F: FnMut(&K, &V) -> CK,
-        CK: Ord,
-    {
-        self.min_by(|key, v1, v2| f(key, v1).cmp(&f(key, v2)))
-    }
-
-    /// Groups elements from the `GroupingMap` source by key and find the maximum and minimum of
-    /// each group.
-    ///
-    /// If several elements are equally maximum, the last element is picked.
-    /// If several elements are equally minimum, the first element is picked.
-    ///
-    /// See [`Itertools::minmax`](crate::Itertools::minmax) for the non-grouping version.
-    ///
-    /// Differences from the non grouping version:
-    /// - It never produces a `MinMaxResult::NoElements`
-    /// - It doesn't have any speedup
-    ///
-    /// Returns a `HashMap` associating the key of each group with the minimum and maximum of that group's elements.
-    ///
-    /// ```
-    /// use itertools::Itertools;
-    /// use itertools::MinMaxResult::{OneElement, MinMax};
-    ///
-    /// let lookup = vec![1, 3, 4, 5, 7, 9, 12].into_iter()
-    ///     .into_grouping_map_by(|&n| n % 3)
-    ///     .minmax();
-    ///
-    /// assert_eq!(lookup[&0], MinMax(3, 12));
-    /// assert_eq!(lookup[&1], MinMax(1, 7));
-    /// assert_eq!(lookup[&2], OneElement(5));
-    /// assert_eq!(lookup.len(), 3);
-    /// ```
-    pub fn minmax(self) -> HashMap<K, MinMaxResult<V>>
-    where
-        V: Ord,
-    {
-        self.minmax_by(|_, v1, v2| V::cmp(v1, v2))
-    }
-
-    /// Groups elements from the `GroupingMap` source by key and find the maximum and minimum of
-    /// each group with respect to the specified comparison function.
-    ///
-    /// If several elements are equally maximum, the last element is picked.
-    /// If several elements are equally minimum, the first element is picked.
-    ///
-    /// It has the same differences from the non-grouping version as `minmax`.
-    ///
-    /// Returns a `HashMap` associating the key of each group with the minimum and maximum of that group's elements.
-    ///
-    /// ```
-    /// use itertools::Itertools;
-    /// use itertools::MinMaxResult::{OneElement, MinMax};
-    ///
-    /// let lookup = vec![1, 3, 4, 5, 7, 9, 12].into_iter()
-    ///     .into_grouping_map_by(|&n| n % 3)
-    ///     .minmax_by(|_key, x, y| y.cmp(x));
-    ///
-    /// assert_eq!(lookup[&0], MinMax(12, 3));
-    /// assert_eq!(lookup[&1], MinMax(7, 1));
-    /// assert_eq!(lookup[&2], OneElement(5));
-    /// assert_eq!(lookup.len(), 3);
-    /// ```
-    pub fn minmax_by<F>(self, mut compare: F) -> HashMap<K, MinMaxResult<V>>
-    where
-        F: FnMut(&K, &V, &V) -> Ordering,
-    {
-        self.aggregate(|acc, key, val| {
-            Some(match acc {
-                Some(MinMaxResult::OneElement(e)) => {
-                    if compare(key, &val, &e) == Ordering::Less {
-                        MinMaxResult::MinMax(val, e)
-                    } else {
-                        MinMaxResult::MinMax(e, val)
-                    }
-                }
-                Some(MinMaxResult::MinMax(min, max)) => {
-                    if compare(key, &val, &min) == Ordering::Less {
-                        MinMaxResult::MinMax(val, max)
-                    } else if compare(key, &val, &max) != Ordering::Less {
-                        MinMaxResult::MinMax(min, val)
-                    } else {
-                        MinMaxResult::MinMax(min, max)
-                    }
-                }
-                None => MinMaxResult::OneElement(val),
-                Some(MinMaxResult::NoElements) => unreachable!(),
-            })
-        })
-    }
-
-    /// Groups elements from the `GroupingMap` source by key and find the elements of each group
-    /// that gives the minimum and maximum from the specified function.
-    ///
-    /// If several elements are equally maximum, the last element is picked.
-    /// If several elements are equally minimum, the first element is picked.
-    ///
-    /// It has the same differences from the non-grouping version as `minmax`.
-    ///
-    /// Returns a `HashMap` associating the key of each group with the minimum and maximum of that group's elements.
-    ///
-    /// ```
-    /// use itertools::Itertools;
-    /// use itertools::MinMaxResult::{OneElement, MinMax};
-    ///
-    /// let lookup = vec![1, 3, 4, 5, 7, 9, 12].into_iter()
-    ///     .into_grouping_map_by(|&n| n % 3)
-    ///     .minmax_by_key(|_key, &val| val % 4);
-    ///
-    /// assert_eq!(lookup[&0], MinMax(12, 3));
-    /// assert_eq!(lookup[&1], MinMax(4, 7));
-    /// assert_eq!(lookup[&2], OneElement(5));
-    /// assert_eq!(lookup.len(), 3);
-    /// ```
-    pub fn minmax_by_key<F, CK>(self, mut f: F) -> HashMap<K, MinMaxResult<V>>
-    where
-        F: FnMut(&K, &V) -> CK,
-        CK: Ord,
-    {
-        self.minmax_by(|key, v1, v2| f(key, v1).cmp(&f(key, v2)))
-    }
-
-    /// Groups elements from the `GroupingMap` source by key and sums them.
-    ///
-    /// This is just a shorthand for `self.reduce(|acc, _, val| acc + val)`.
-    /// It is more limited than `Iterator::sum` since it doesn't use the `Sum` trait.
-    ///
-    /// Returns a `HashMap` associating the key of each group with the sum of that group's elements.
-    ///
-    /// ```
-    /// use itertools::Itertools;
-    ///
-    /// let lookup = vec![1, 3, 4, 5, 7, 8, 9, 12].into_iter()
-    ///     .into_grouping_map_by(|&n| n % 3)
-    ///     .sum();
-    ///
-    /// assert_eq!(lookup[&0], 3 + 9 + 12);
-    /// assert_eq!(lookup[&1], 1 + 4 + 7);
-    /// assert_eq!(lookup[&2], 5 + 8);
-    /// assert_eq!(lookup.len(), 3);
-    /// ```
-    pub fn sum(self) -> HashMap<K, V>
-    where
-        V: Add<V, Output = V>,
-    {
-        self.reduce(|acc, _, val| acc + val)
-    }
-
-    /// Groups elements from the `GroupingMap` source by key and multiply them.
-    ///
-    /// This is just a shorthand for `self.reduce(|acc, _, val| acc * val)`.
-    /// It is more limited than `Iterator::product` since it doesn't use the `Product` trait.
-    ///
-    /// Returns a `HashMap` associating the key of each group with the product of that group's elements.
-    ///
-    /// ```
-    /// use itertools::Itertools;
-    ///
-    /// let lookup = vec![1, 3, 4, 5, 7, 8, 9, 12].into_iter()
-    ///     .into_grouping_map_by(|&n| n % 3)
-    ///     .product();
-    ///
-    /// assert_eq!(lookup[&0], 3 * 9 * 12);
-    /// assert_eq!(lookup[&1], 1 * 4 * 7);
-    /// assert_eq!(lookup[&2], 5 * 8);
-    /// assert_eq!(lookup.len(), 3);
-    /// ```
-    pub fn product(self) -> HashMap<K, V>
-    where
-        V: Mul<V, Output = V>,
-    {
-        self.reduce(|acc, _, val| acc * val)
-    }
-}