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, 37 insertions, 0 deletions

diff --git a/vendor/github.com/authzed/grpcutil/DCO b/vendor/github.com/authzed/grpcutil/DCO
new file mode 100644
index 00000000..8201f992
--- /dev/null
+++ b/vendor/github.com/authzed/grpcutil/DCO
@@ -0,0 +1,37 @@
+Developer Certificate of Origin
+Version 1.1
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+Developer's Certificate of Origin 1.1
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