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, 10 insertions, 0 deletions

diff --git a/etc/authzd/spice.schema b/etc/authzd/spice.schema
index 0d6a6482..da408b80 100644
--- a/etc/authzd/spice.schema
+++ b/etc/authzd/spice.schema
@@ -1,7 +1,17 @@
 definition user {}
+
 definition project {
   relation developer: user
   relation maintainer: user
+
+  permission read = developer + maintainer
+  permission write = maintainer
+}
+
+definition group {
+  relation developer: user
+  relation maintainer: user
+
   permission read = developer + maintainer
   permission write = maintainer
 }