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, 57 deletions

diff --git a/vendor/ref-cast/src/custom.rs b/vendor/ref-cast/src/custom.rs
deleted file mode 100644
index 76725bcf..00000000
--- a/vendor/ref-cast/src/custom.rs
+++ /dev/null
@@ -1,57 +0,0 @@
-// Not public API. Use #[derive(RefCastCustom)] and #[ref_cast_custom].
-#[doc(hidden)]
-pub unsafe trait RefCastCustom<From: ?Sized> {
-    type CurrentCrate;
-    fn __static_assert() {}
-}
-
-#[doc(hidden)]
-pub unsafe trait RefCastOkay<From>: Sealed<From> {
-    type CurrentCrate;
-    type Target: ?Sized;
-}
-
-unsafe impl<'a, From, To> RefCastOkay<&'a From> for &'a To
-where
-    From: ?Sized,
-    To: ?Sized + RefCastCustom<From>,
-{
-    type CurrentCrate = To::CurrentCrate;
-    type Target = To;
-}
-
-unsafe impl<'a, From, To> RefCastOkay<&'a mut From> for &'a mut To
-where
-    From: ?Sized,
-    To: ?Sized + RefCastCustom<From>,
-{
-    type CurrentCrate = To::CurrentCrate;
-    type Target = To;
-}
-
-#[doc(hidden)]
-pub trait Sealed<From> {}
-
-impl<'a, From, To> Sealed<&'a From> for &'a To
-where
-    From: ?Sized,
-    To: ?Sized + RefCastCustom<From>,
-{
-}
-
-impl<'a, From, To> Sealed<&'a mut From> for &'a mut To
-where
-    From: ?Sized,
-    To: ?Sized + RefCastCustom<From>,
-{
-}
-
-#[doc(hidden)]
-pub type CurrentCrate<From, To> = <To as RefCastOkay<From>>::CurrentCrate;
-
-#[doc(hidden)]
-pub fn ref_cast_custom<From, To>(_arg: From)
-where
-    To: RefCastOkay<From>,
-{
-}