Chain-aware (A2A) authorization using OPA as a sidecar pattern

I keep getting queries about A2A authorization and where should it sit, whether it should be done by AI Gateway and what is a better pattern. We at Leanroute, think that OPA as a sidecar pattern is suitable for this chain-aware of authorization. Thoughts? https://leanroute.dev/blog/chain-aware-authorization-opa-sidecar-mcp