I would be interested to see an example of how a gRPC-based service could implement https://github.com/googleapis/googleapis/blob/master/google/iam/v1/iam_policy.proto and back the implementation with calls to spicedb. It would be great to take something like https://github.com/GoogleCloudPlatform/python-docs-samples/blob/main/endpoints/bookstore-grpc/bookstore.proto and extend the proto with IAM.