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, 27 deletions

diff --git a/vendor/itertools/src/concat_impl.rs b/vendor/itertools/src/concat_impl.rs
deleted file mode 100644
index dc80839c..00000000
--- a/vendor/itertools/src/concat_impl.rs
+++ /dev/null
@@ -1,27 +0,0 @@
-/// Combine all an iterator's elements into one element by using [`Extend`].
-///
-/// [`IntoIterator`]-enabled version of [`Itertools::concat`](crate::Itertools::concat).
-///
-/// This combinator will extend the first item with each of the rest of the
-/// items of the iterator. If the iterator is empty, the default value of
-/// `I::Item` is returned.
-///
-/// ```rust
-/// use itertools::concat;
-///
-/// let input = vec![vec![1], vec![2, 3], vec![4, 5, 6]];
-/// assert_eq!(concat(input), vec![1, 2, 3, 4, 5, 6]);
-/// ```
-pub fn concat<I>(iterable: I) -> I::Item
-where
-    I: IntoIterator,
-    I::Item: Extend<<<I as IntoIterator>::Item as IntoIterator>::Item> + IntoIterator + Default,
-{
-    iterable
-        .into_iter()
-        .reduce(|mut a, b| {
-            a.extend(b);
-            a
-        })
-        .unwrap_or_default()
-}