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, 60 deletions

diff --git a/vendor/syn/src/thread.rs b/vendor/syn/src/thread.rs
deleted file mode 100644
index b33d248a..00000000
--- a/vendor/syn/src/thread.rs
+++ /dev/null
@@ -1,60 +0,0 @@
-use std::fmt::{self, Debug};
-use std::thread::{self, ThreadId};
-
-/// ThreadBound is a Sync-maker and Send-maker that allows accessing a value
-/// of type T only from the original thread on which the ThreadBound was
-/// constructed.
-pub(crate) struct ThreadBound<T> {
-    value: T,
-    thread_id: ThreadId,
-}
-
-unsafe impl<T> Sync for ThreadBound<T> {}
-
-// Send bound requires Copy, as otherwise Drop could run in the wrong place.
-//
-// Today Copy and Drop are mutually exclusive so `T: Copy` implies `T: !Drop`.
-// This impl needs to be revisited if that restriction is relaxed in the future.
-unsafe impl<T: Copy> Send for ThreadBound<T> {}
-
-impl<T> ThreadBound<T> {
-    pub(crate) fn new(value: T) -> Self {
-        ThreadBound {
-            value,
-            thread_id: thread::current().id(),
-        }
-    }
-
-    pub(crate) fn get(&self) -> Option<&T> {
-        if thread::current().id() == self.thread_id {
-            Some(&self.value)
-        } else {
-            None
-        }
-    }
-}
-
-impl<T: Debug> Debug for ThreadBound<T> {
-    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
-        match self.get() {
-            Some(value) => Debug::fmt(value, formatter),
-            None => formatter.write_str("unknown"),
-        }
-    }
-}
-
-// Copy the bytes of T, even if the currently running thread is the "wrong"
-// thread. This is fine as long as the original thread is not simultaneously
-// mutating this value via interior mutability, which would be a data race.
-//
-// Currently `T: Copy` is sufficient to guarantee that T contains no interior
-// mutability, because _all_ interior mutability in Rust is built on
-// std::cell::UnsafeCell, which has no Copy impl. This impl needs to be
-// revisited if that restriction is relaxed in the future.
-impl<T: Copy> Copy for ThreadBound<T> {}
-
-impl<T: Copy> Clone for ThreadBound<T> {
-    fn clone(&self) -> Self {
-        *self
-    }
-}