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, 16 deletions

diff --git a/vendor/tower/src/buffer/message.rs b/vendor/tower/src/buffer/message.rs
deleted file mode 100644
index 6d13aa12..00000000
--- a/vendor/tower/src/buffer/message.rs
+++ /dev/null
@@ -1,16 +0,0 @@
-use super::error::ServiceError;
-use tokio::sync::oneshot;
-
-/// Message sent over buffer
-#[derive(Debug)]
-pub(crate) struct Message<Request, Fut> {
-    pub(crate) request: Request,
-    pub(crate) tx: Tx<Fut>,
-    pub(crate) span: tracing::Span,
-}
-
-/// Response sender
-pub(crate) type Tx<Fut> = oneshot::Sender<Result<Fut, ServiceError>>;
-
-/// Response receiver
-pub(crate) type Rx<Fut> = oneshot::Receiver<Result<Fut, ServiceError>>;