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.

3 files changed, 0 insertions, 686 deletions

diff --git a/vendor/hex/src/error.rs b/vendor/hex/src/error.rs
deleted file mode 100644
index ff7a3b5c..00000000
--- a/vendor/hex/src/error.rs
+++ /dev/null
@@ -1,59 +0,0 @@
-use core::fmt;
-
-/// The error type for decoding a hex string into `Vec<u8>` or `[u8; N]`.
-#[derive(Debug, Clone, Copy, PartialEq)]
-pub enum FromHexError {
-    /// An invalid character was found. Valid ones are: `0...9`, `a...f`
-    /// or `A...F`.
-    InvalidHexCharacter { c: char, index: usize },
-
-    /// A hex string's length needs to be even, as two digits correspond to
-    /// one byte.
-    OddLength,
-
-    /// If the hex string is decoded into a fixed sized container, such as an
-    /// array, the hex string's length * 2 has to match the container's
-    /// length.
-    InvalidStringLength,
-}
-
-#[cfg(feature = "std")]
-impl std::error::Error for FromHexError {}
-
-impl fmt::Display for FromHexError {
-    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        match *self {
-            FromHexError::InvalidHexCharacter { c, index } => {
-                write!(f, "Invalid character {:?} at position {}", c, index)
-            }
-            FromHexError::OddLength => write!(f, "Odd number of digits"),
-            FromHexError::InvalidStringLength => write!(f, "Invalid string length"),
-        }
-    }
-}
-
-#[cfg(test)]
-// this feature flag is here to suppress unused
-// warnings of `super::*` and `pretty_assertions::assert_eq`
-#[cfg(feature = "alloc")]
-mod tests {
-    use super::*;
-    #[cfg(feature = "alloc")]
-    use alloc::string::ToString;
-    use pretty_assertions::assert_eq;
-
-    #[test]
-    #[cfg(feature = "alloc")]
-    fn test_display() {
-        assert_eq!(
-            FromHexError::InvalidHexCharacter { c: '\n', index: 5 }.to_string(),
-            "Invalid character '\\n' at position 5"
-        );
-
-        assert_eq!(FromHexError::OddLength.to_string(), "Odd number of digits");
-        assert_eq!(
-            FromHexError::InvalidStringLength.to_string(),
-            "Invalid string length"
-        );
-    }
-}
diff --git a/vendor/hex/src/lib.rs b/vendor/hex/src/lib.rs
deleted file mode 100644
index ec48961b..00000000
--- a/vendor/hex/src/lib.rs
+++ /dev/null
@@ -1,525 +0,0 @@
-// Copyright (c) 2013-2014 The Rust Project Developers.
-// Copyright (c) 2015-2020 The rust-hex Developers.
-//
-// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
-// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
-// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
-// option. This file may not be copied, modified, or distributed
-// except according to those terms.
-//! Encoding and decoding hex strings.
-//!
-//! For most cases, you can simply use the [`decode`], [`encode`] and
-//! [`encode_upper`] functions. If you need a bit more control, use the traits
-//! [`ToHex`] and [`FromHex`] instead.
-//!
-//! # Example
-//!
-//! ```
-//! # #[cfg(not(feature = "alloc"))]
-//! # let mut output = [0; 0x18];
-//! #
-//! # #[cfg(not(feature = "alloc"))]
-//! # hex::encode_to_slice(b"Hello world!", &mut output).unwrap();
-//! #
-//! # #[cfg(not(feature = "alloc"))]
-//! # let hex_string = ::core::str::from_utf8(&output).unwrap();
-//! #
-//! # #[cfg(feature = "alloc")]
-//! let hex_string = hex::encode("Hello world!");
-//!
-//! println!("{}", hex_string); // Prints "48656c6c6f20776f726c6421"
-//!
-//! # assert_eq!(hex_string, "48656c6c6f20776f726c6421");
-//! ```
-
-#![doc(html_root_url = "https://docs.rs/hex/0.4.3")]
-#![cfg_attr(not(feature = "std"), no_std)]
-#![cfg_attr(docsrs, feature(doc_cfg))]
-#![allow(clippy::unreadable_literal)]
-
-#[cfg(feature = "alloc")]
-extern crate alloc;
-#[cfg(feature = "alloc")]
-use alloc::{string::String, vec::Vec};
-
-use core::iter;
-
-mod error;
-pub use crate::error::FromHexError;
-
-#[cfg(feature = "serde")]
-#[cfg_attr(docsrs, doc(cfg(feature = "serde")))]
-pub mod serde;
-#[cfg(feature = "serde")]
-pub use crate::serde::deserialize;
-#[cfg(all(feature = "alloc", feature = "serde"))]
-pub use crate::serde::{serialize, serialize_upper};
-
-/// Encoding values as hex string.
-///
-/// This trait is implemented for all `T` which implement `AsRef<[u8]>`. This
-/// includes `String`, `str`, `Vec<u8>` and `[u8]`.
-///
-/// # Example
-///
-/// ```
-/// use hex::ToHex;
-///
-/// println!("{}", "Hello world!".encode_hex::<String>());
-/// # assert_eq!("Hello world!".encode_hex::<String>(), "48656c6c6f20776f726c6421".to_string());
-/// ```
-///
-/// *Note*: instead of using this trait, you might want to use [`encode()`].
-pub trait ToHex {
-    /// Encode the hex strict representing `self` into the result. Lower case
-    /// letters are used (e.g. `f9b4ca`)
-    fn encode_hex<T: iter::FromIterator<char>>(&self) -> T;
-
-    /// Encode the hex strict representing `self` into the result. Upper case
-    /// letters are used (e.g. `F9B4CA`)
-    fn encode_hex_upper<T: iter::FromIterator<char>>(&self) -> T;
-}
-
-const HEX_CHARS_LOWER: &[u8; 16] = b"0123456789abcdef";
-const HEX_CHARS_UPPER: &[u8; 16] = b"0123456789ABCDEF";
-
-struct BytesToHexChars<'a> {
-    inner: ::core::slice::Iter<'a, u8>,
-    table: &'static [u8; 16],
-    next: Option<char>,
-}
-
-impl<'a> BytesToHexChars<'a> {
-    fn new(inner: &'a [u8], table: &'static [u8; 16]) -> BytesToHexChars<'a> {
-        BytesToHexChars {
-            inner: inner.iter(),
-            table,
-            next: None,
-        }
-    }
-}
-
-impl<'a> Iterator for BytesToHexChars<'a> {
-    type Item = char;
-
-    fn next(&mut self) -> Option<Self::Item> {
-        match self.next.take() {
-            Some(current) => Some(current),
-            None => self.inner.next().map(|byte| {
-                let current = self.table[(byte >> 4) as usize] as char;
-                self.next = Some(self.table[(byte & 0x0F) as usize] as char);
-                current
-            }),
-        }
-    }
-
-    fn size_hint(&self) -> (usize, Option<usize>) {
-        let length = self.len();
-        (length, Some(length))
-    }
-}
-
-impl<'a> iter::ExactSizeIterator for BytesToHexChars<'a> {
-    fn len(&self) -> usize {
-        let mut length = self.inner.len() * 2;
-        if self.next.is_some() {
-            length += 1;
-        }
-        length
-    }
-}
-
-#[inline]
-fn encode_to_iter<T: iter::FromIterator<char>>(table: &'static [u8; 16], source: &[u8]) -> T {
-    BytesToHexChars::new(source, table).collect()
-}
-
-impl<T: AsRef<[u8]>> ToHex for T {
-    fn encode_hex<U: iter::FromIterator<char>>(&self) -> U {
-        encode_to_iter(HEX_CHARS_LOWER, self.as_ref())
-    }
-
-    fn encode_hex_upper<U: iter::FromIterator<char>>(&self) -> U {
-        encode_to_iter(HEX_CHARS_UPPER, self.as_ref())
-    }
-}
-
-/// Types that can be decoded from a hex string.
-///
-/// This trait is implemented for `Vec<u8>` and small `u8`-arrays.
-///
-/// # Example
-///
-/// ```
-/// use core::str;
-/// use hex::FromHex;
-///
-/// let buffer = <[u8; 12]>::from_hex("48656c6c6f20776f726c6421")?;
-/// let string = str::from_utf8(&buffer).expect("invalid buffer length");
-///
-/// println!("{}", string); // prints "Hello world!"
-/// # assert_eq!("Hello world!", string);
-/// # Ok::<(), hex::FromHexError>(())
-/// ```
-pub trait FromHex: Sized {
-    type Error;
-
-    /// Creates an instance of type `Self` from the given hex string, or fails
-    /// with a custom error type.
-    ///
-    /// Both, upper and lower case characters are valid and can even be
-    /// mixed (e.g. `f9b4ca`, `F9B4CA` and `f9B4Ca` are all valid strings).
-    fn from_hex<T: AsRef<[u8]>>(hex: T) -> Result<Self, Self::Error>;
-}
-
-fn val(c: u8, idx: usize) -> Result<u8, FromHexError> {
-    match c {
-        b'A'..=b'F' => Ok(c - b'A' + 10),
-        b'a'..=b'f' => Ok(c - b'a' + 10),
-        b'0'..=b'9' => Ok(c - b'0'),
-        _ => Err(FromHexError::InvalidHexCharacter {
-            c: c as char,
-            index: idx,
-        }),
-    }
-}
-
-#[cfg(feature = "alloc")]
-impl FromHex for Vec<u8> {
-    type Error = FromHexError;
-
-    fn from_hex<T: AsRef<[u8]>>(hex: T) -> Result<Self, Self::Error> {
-        let hex = hex.as_ref();
-        if hex.len() % 2 != 0 {
-            return Err(FromHexError::OddLength);
-        }
-
-        hex.chunks(2)
-            .enumerate()
-            .map(|(i, pair)| Ok(val(pair[0], 2 * i)? << 4 | val(pair[1], 2 * i + 1)?))
-            .collect()
-    }
-}
-
-// Helper macro to implement the trait for a few fixed sized arrays. Once Rust
-// has type level integers, this should be removed.
-macro_rules! from_hex_array_impl {
-    ($($len:expr)+) => {$(
-        impl FromHex for [u8; $len] {
-            type Error = FromHexError;
-
-            fn from_hex<T: AsRef<[u8]>>(hex: T) -> Result<Self, Self::Error> {
-                let mut out = [0_u8; $len];
-                decode_to_slice(hex, &mut out as &mut [u8])?;
-                Ok(out)
-            }
-        }
-    )+}
-}
-
-from_hex_array_impl! {
-    1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
-    17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32
-    33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48
-    49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64
-    65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80
-    81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96
-    97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112
-    113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128
-    160 192 200 224 256 384 512 768 1024 2048 4096 8192 16384 32768
-}
-
-#[cfg(any(target_pointer_width = "32", target_pointer_width = "64"))]
-from_hex_array_impl! {
-    65536 131072 262144 524288 1048576 2097152 4194304 8388608
-    16777216 33554432 67108864 134217728 268435456 536870912
-    1073741824 2147483648
-}
-
-#[cfg(target_pointer_width = "64")]
-from_hex_array_impl! {
-    4294967296
-}
-
-/// Encodes `data` as hex string using lowercase characters.
-///
-/// Lowercase characters are used (e.g. `f9b4ca`). The resulting string's
-/// length is always even, each byte in `data` is always encoded using two hex
-/// digits. Thus, the resulting string contains exactly twice as many bytes as
-/// the input data.
-///
-/// # Example
-///
-/// ```
-/// assert_eq!(hex::encode("Hello world!"), "48656c6c6f20776f726c6421");
-/// assert_eq!(hex::encode(vec![1, 2, 3, 15, 16]), "0102030f10");
-/// ```
-#[must_use]
-#[cfg(feature = "alloc")]
-pub fn encode<T: AsRef<[u8]>>(data: T) -> String {
-    data.encode_hex()
-}
-
-/// Encodes `data` as hex string using uppercase characters.
-///
-/// Apart from the characters' casing, this works exactly like `encode()`.
-///
-/// # Example
-///
-/// ```
-/// assert_eq!(hex::encode_upper("Hello world!"), "48656C6C6F20776F726C6421");
-/// assert_eq!(hex::encode_upper(vec![1, 2, 3, 15, 16]), "0102030F10");
-/// ```
-#[must_use]
-#[cfg(feature = "alloc")]
-pub fn encode_upper<T: AsRef<[u8]>>(data: T) -> String {
-    data.encode_hex_upper()
-}
-
-/// Decodes a hex string into raw bytes.
-///
-/// Both, upper and lower case characters are valid in the input string and can
-/// even be mixed (e.g. `f9b4ca`, `F9B4CA` and `f9B4Ca` are all valid strings).
-///
-/// # Example
-///
-/// ```
-/// assert_eq!(
-///     hex::decode("48656c6c6f20776f726c6421"),
-///     Ok("Hello world!".to_owned().into_bytes())
-/// );
-///
-/// assert_eq!(hex::decode("123"), Err(hex::FromHexError::OddLength));
-/// assert!(hex::decode("foo").is_err());
-/// ```
-#[cfg(feature = "alloc")]
-pub fn decode<T: AsRef<[u8]>>(data: T) -> Result<Vec<u8>, FromHexError> {
-    FromHex::from_hex(data)
-}
-
-/// Decode a hex string into a mutable bytes slice.
-///
-/// Both, upper and lower case characters are valid in the input string and can
-/// even be mixed (e.g. `f9b4ca`, `F9B4CA` and `f9B4Ca` are all valid strings).
-///
-/// # Example
-///
-/// ```
-/// let mut bytes = [0u8; 4];
-/// assert_eq!(hex::decode_to_slice("6b697769", &mut bytes as &mut [u8]), Ok(()));
-/// assert_eq!(&bytes, b"kiwi");
-/// ```
-pub fn decode_to_slice<T: AsRef<[u8]>>(data: T, out: &mut [u8]) -> Result<(), FromHexError> {
-    let data = data.as_ref();
-
-    if data.len() % 2 != 0 {
-        return Err(FromHexError::OddLength);
-    }
-    if data.len() / 2 != out.len() {
-        return Err(FromHexError::InvalidStringLength);
-    }
-
-    for (i, byte) in out.iter_mut().enumerate() {
-        *byte = val(data[2 * i], 2 * i)? << 4 | val(data[2 * i + 1], 2 * i + 1)?;
-    }
-
-    Ok(())
-}
-
-// generates an iterator like this
-// (0, 1)
-// (2, 3)
-// (4, 5)
-// (6, 7)
-// ...
-#[inline]
-fn generate_iter(len: usize) -> impl Iterator<Item = (usize, usize)> {
-    (0..len).step_by(2).zip((0..len).skip(1).step_by(2))
-}
-
-// the inverse of `val`.
-#[inline]
-#[must_use]
-fn byte2hex(byte: u8, table: &[u8; 16]) -> (u8, u8) {
-    let high = table[((byte & 0xf0) >> 4) as usize];
-    let low = table[(byte & 0x0f) as usize];
-
-    (high, low)
-}
-
-/// Encodes some bytes into a mutable slice of bytes.
-///
-/// The output buffer, has to be able to hold at least `input.len() * 2` bytes,
-/// otherwise this function will return an error.
-///
-/// # Example
-///
-/// ```
-/// # use hex::FromHexError;
-/// # fn main() -> Result<(), FromHexError> {
-/// let mut bytes = [0u8; 4 * 2];
-///
-/// hex::encode_to_slice(b"kiwi", &mut bytes)?;
-/// assert_eq!(&bytes, b"6b697769");
-/// # Ok(())
-/// # }
-/// ```
-pub fn encode_to_slice<T: AsRef<[u8]>>(input: T, output: &mut [u8]) -> Result<(), FromHexError> {
-    if input.as_ref().len() * 2 != output.len() {
-        return Err(FromHexError::InvalidStringLength);
-    }
-
-    for (byte, (i, j)) in input
-        .as_ref()
-        .iter()
-        .zip(generate_iter(input.as_ref().len() * 2))
-    {
-        let (high, low) = byte2hex(*byte, HEX_CHARS_LOWER);
-        output[i] = high;
-        output[j] = low;
-    }
-
-    Ok(())
-}
-
-#[cfg(test)]
-mod test {
-    use super::*;
-    #[cfg(feature = "alloc")]
-    use alloc::string::ToString;
-    use pretty_assertions::assert_eq;
-
-    #[test]
-    #[cfg(feature = "alloc")]
-    fn test_gen_iter() {
-        let result = vec![(0, 1), (2, 3)];
-
-        assert_eq!(generate_iter(5).collect::<Vec<_>>(), result);
-    }
-
-    #[test]
-    fn test_encode_to_slice() {
-        let mut output_1 = [0; 4 * 2];
-        encode_to_slice(b"kiwi", &mut output_1).unwrap();
-        assert_eq!(&output_1, b"6b697769");
-
-        let mut output_2 = [0; 5 * 2];
-        encode_to_slice(b"kiwis", &mut output_2).unwrap();
-        assert_eq!(&output_2, b"6b69776973");
-
-        let mut output_3 = [0; 100];
-
-        assert_eq!(
-            encode_to_slice(b"kiwis", &mut output_3),
-            Err(FromHexError::InvalidStringLength)
-        );
-    }
-
-    #[test]
-    fn test_decode_to_slice() {
-        let mut output_1 = [0; 4];
-        decode_to_slice(b"6b697769", &mut output_1).unwrap();
-        assert_eq!(&output_1, b"kiwi");
-
-        let mut output_2 = [0; 5];
-        decode_to_slice(b"6b69776973", &mut output_2).unwrap();
-        assert_eq!(&output_2, b"kiwis");
-
-        let mut output_3 = [0; 4];
-
-        assert_eq!(
-            decode_to_slice(b"6", &mut output_3),
-            Err(FromHexError::OddLength)
-        );
-    }
-
-    #[test]
-    #[cfg(feature = "alloc")]
-    fn test_encode() {
-        assert_eq!(encode("foobar"), "666f6f626172");
-    }
-
-    #[test]
-    #[cfg(feature = "alloc")]
-    fn test_decode() {
-        assert_eq!(
-            decode("666f6f626172"),
-            Ok(String::from("foobar").into_bytes())
-        );
-    }
-
-    #[test]
-    #[cfg(feature = "alloc")]
-    pub fn test_from_hex_okay_str() {
-        assert_eq!(Vec::from_hex("666f6f626172").unwrap(), b"foobar");
-        assert_eq!(Vec::from_hex("666F6F626172").unwrap(), b"foobar");
-    }
-
-    #[test]
-    #[cfg(feature = "alloc")]
-    pub fn test_from_hex_okay_bytes() {
-        assert_eq!(Vec::from_hex(b"666f6f626172").unwrap(), b"foobar");
-        assert_eq!(Vec::from_hex(b"666F6F626172").unwrap(), b"foobar");
-    }
-
-    #[test]
-    #[cfg(feature = "alloc")]
-    pub fn test_invalid_length() {
-        assert_eq!(Vec::from_hex("1").unwrap_err(), FromHexError::OddLength);
-        assert_eq!(
-            Vec::from_hex("666f6f6261721").unwrap_err(),
-            FromHexError::OddLength
-        );
-    }
-
-    #[test]
-    #[cfg(feature = "alloc")]
-    pub fn test_invalid_char() {
-        assert_eq!(
-            Vec::from_hex("66ag").unwrap_err(),
-            FromHexError::InvalidHexCharacter { c: 'g', index: 3 }
-        );
-    }
-
-    #[test]
-    #[cfg(feature = "alloc")]
-    pub fn test_empty() {
-        assert_eq!(Vec::from_hex("").unwrap(), b"");
-    }
-
-    #[test]
-    #[cfg(feature = "alloc")]
-    pub fn test_from_hex_whitespace() {
-        assert_eq!(
-            Vec::from_hex("666f 6f62617").unwrap_err(),
-            FromHexError::InvalidHexCharacter { c: ' ', index: 4 }
-        );
-    }
-
-    #[test]
-    pub fn test_from_hex_array() {
-        assert_eq!(
-            <[u8; 6] as FromHex>::from_hex("666f6f626172"),
-            Ok([0x66, 0x6f, 0x6f, 0x62, 0x61, 0x72])
-        );
-
-        assert_eq!(
-            <[u8; 5] as FromHex>::from_hex("666f6f626172"),
-            Err(FromHexError::InvalidStringLength)
-        );
-    }
-
-    #[test]
-    #[cfg(feature = "alloc")]
-    fn test_to_hex() {
-        assert_eq!(
-            [0x66, 0x6f, 0x6f, 0x62, 0x61, 0x72].encode_hex::<String>(),
-            "666f6f626172".to_string(),
-        );
-
-        assert_eq!(
-            [0x66, 0x6f, 0x6f, 0x62, 0x61, 0x72].encode_hex_upper::<String>(),
-            "666F6F626172".to_string(),
-        );
-    }
-}
diff --git a/vendor/hex/src/serde.rs b/vendor/hex/src/serde.rs
deleted file mode 100644
index 335a1513..00000000
--- a/vendor/hex/src/serde.rs
+++ /dev/null
@@ -1,102 +0,0 @@
-//! Hex encoding with `serde`.
-#[cfg_attr(
-    all(feature = "alloc", feature = "serde"),
-    doc = r##"
-# Example
-
-```
-use serde::{Serialize, Deserialize};
-
-#[derive(Serialize, Deserialize)]
-struct Foo {
-    #[serde(with = "hex")]
-    bar: Vec<u8>,
-}
-```
-"##
-)]
-use serde::de::{Error, Visitor};
-use serde::Deserializer;
-#[cfg(feature = "alloc")]
-use serde::Serializer;
-
-#[cfg(feature = "alloc")]
-use alloc::string::String;
-
-use core::fmt;
-use core::marker::PhantomData;
-
-use crate::FromHex;
-
-#[cfg(feature = "alloc")]
-use crate::ToHex;
-
-/// Serializes `data` as hex string using uppercase characters.
-///
-/// Apart from the characters' casing, this works exactly like `serialize()`.
-#[cfg(feature = "alloc")]
-pub fn serialize_upper<S, T>(data: T, serializer: S) -> Result<S::Ok, S::Error>
-where
-    S: Serializer,
-    T: ToHex,
-{
-    let s = data.encode_hex_upper::<String>();
-    serializer.serialize_str(&s)
-}
-
-/// Serializes `data` as hex string using lowercase characters.
-///
-/// Lowercase characters are used (e.g. `f9b4ca`). The resulting string's length
-/// is always even, each byte in data is always encoded using two hex digits.
-/// Thus, the resulting string contains exactly twice as many bytes as the input
-/// data.
-#[cfg(feature = "alloc")]
-pub fn serialize<S, T>(data: T, serializer: S) -> Result<S::Ok, S::Error>
-where
-    S: Serializer,
-    T: ToHex,
-{
-    let s = data.encode_hex::<String>();
-    serializer.serialize_str(&s)
-}
-
-/// Deserializes a hex string into raw bytes.
-///
-/// Both, upper and lower case characters are valid in the input string and can
-/// even be mixed (e.g. `f9b4ca`, `F9B4CA` and `f9B4Ca` are all valid strings).
-pub fn deserialize<'de, D, T>(deserializer: D) -> Result<T, D::Error>
-where
-    D: Deserializer<'de>,
-    T: FromHex,
-    <T as FromHex>::Error: fmt::Display,
-{
-    struct HexStrVisitor<T>(PhantomData<T>);
-
-    impl<'de, T> Visitor<'de> for HexStrVisitor<T>
-    where
-        T: FromHex,
-        <T as FromHex>::Error: fmt::Display,
-    {
-        type Value = T;
-
-        fn expecting(&self, f: &mut fmt::Formatter) -> fmt::Result {
-            write!(f, "a hex encoded string")
-        }
-
-        fn visit_str<E>(self, data: &str) -> Result<Self::Value, E>
-        where
-            E: Error,
-        {
-            FromHex::from_hex(data).map_err(Error::custom)
-        }
-
-        fn visit_borrowed_str<E>(self, data: &'de str) -> Result<Self::Value, E>
-        where
-            E: Error,
-        {
-            FromHex::from_hex(data).map_err(Error::custom)
-        }
-    }
-
-    deserializer.deserialize_str(HexStrVisitor(PhantomData))
-}