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, 123 deletions

diff --git a/vendor/ref-cast/README.md b/vendor/ref-cast/README.md
deleted file mode 100644
index 5188ba10..00000000
--- a/vendor/ref-cast/README.md
+++ /dev/null
@@ -1,123 +0,0 @@
-RefCast
-=======
-
-[<img alt="github" src="https://img.shields.io/badge/github-dtolnay/ref--cast-8da0cb?style=for-the-badge&labelColor=555555&logo=github" height="20">](https://github.com/dtolnay/ref-cast)
-[<img alt="crates.io" src="https://img.shields.io/crates/v/ref-cast.svg?style=for-the-badge&color=fc8d62&logo=rust" height="20">](https://crates.io/crates/ref-cast)
-[<img alt="docs.rs" src="https://img.shields.io/badge/docs.rs-ref--cast-66c2a5?style=for-the-badge&labelColor=555555&logo=docs.rs" height="20">](https://docs.rs/ref-cast)
-[<img alt="build status" src="https://img.shields.io/github/actions/workflow/status/dtolnay/ref-cast/ci.yml?branch=master&style=for-the-badge" height="20">](https://github.com/dtolnay/ref-cast/actions?query=branch%3Amaster)
-
-Safely cast `&T` to `&U` where the struct `U` contains a single field of
-type `T`.
-
-```toml
-[dependencies]
-ref-cast = "1.0"
-```
-
-## Basic example
-
-```rust
-use ref_cast::RefCast;
-
-#[derive(RefCast)]
-#[repr(transparent)]
-struct U(String);
-
-fn main() {
-    let s = String::new();
-
-    // Safely cast from `&String` to `&U`.
-    let u = U::ref_cast(&s);
-}
-```
-
-Note that `#[repr(transparent)]` is required in order for the conversion to be
-sound. The derive macro will refuse to compile if that is not present.
-
-## Realistic example
-
-Suppose we have a multidimensional array represented in a flat buffer in
-row-major order for performance reasons, but we want to expose an indexing
-operation that works in column-major order because it is more intuitive in
-the context of our application.
-
-```rust
-const MAP_WIDTH: usize = 4;
-
-struct Tile(u8);
-
-struct TileMap {
-    storage: Vec<Tile>,
-}
-
-// `tilemap[x][y]` should give us `tilemap.storage[y * MAP_WIDTH + x]`.
-```
-
-The signature of the [`Index`] trait in Rust is such that the output is
-forced to be borrowed from the type being indexed. So something like the
-following is not going to work.
-
-[`Index`]: https://doc.rust-lang.org/std/ops/trait.Index.html
-
-```rust
-struct Column<'a> {
-    tilemap: &'a TileMap,
-    x: usize,
-}
-
-// Does not work! The output of Index must be a reference that is
-// borrowed from self. Here the type Column is not a reference.
-impl Index<usize> for TileMap {
-    fn index(&self, x: usize) -> Column {
-        assert!(x < MAP_WIDTH);
-        Column { tilemap: self, x }
-    }
-}
-
-impl<'a> Index<usize> for Column<'a> {
-    fn index(&self, y: usize) -> &Tile {
-        &self.tilemap.storage[y * MAP_WIDTH + self.x]
-    }
-}
-```
-
-Here is a working approach using `RefCast`.
-
-```rust
-#[derive(RefCast)]
-#[repr(transparent)]
-struct Strided([Tile]);
-
-// Implement `tilemap[x][y]` as `tilemap[x..][y * MAP_WIDTH]`.
-impl Index<usize> for TileMap {
-    type Output = Strided;
-    fn index(&self, x: usize) -> &Self::Output {
-        assert!(x < MAP_WIDTH);
-        Strided::ref_cast(&self.storage[x..])
-    }
-}
-
-impl Index<usize> for Strided {
-    type Output = Tile;
-    fn index(&self, y: usize) -> &Self::Output {
-        &self.0[y * MAP_WIDTH]
-    }
-}
-```
-
-<br>
-
-#### License
-
-<sup>
-Licensed under either of <a href="LICENSE-APACHE">Apache License, Version
-2.0</a> or <a href="LICENSE-MIT">MIT license</a> at your option.
-</sup>
-
-<br>
-
-<sub>
-Unless you explicitly state otherwise, any contribution intentionally submitted
-for inclusion in this crate by you, as defined in the Apache-2.0 license, shall
-be dual licensed as above, without any additional terms or conditions.
-</sub>