Consider using/supporting `google.api.HttpRule` `MethodOptions` extension

[micolous]

grpc-api-gateway defines two different google.protobuf.MethodOptions extensions. ProtoEndpointBindings looks like a type which is to be used in a similar way to google.api.HttpRule:

grpc-api-gateway/api/meshapi/gateway/annotations.proto

Lines 24 to 25 in 076dc47

	// ID assigned by protobuf-global-extension-registry@google.com for gRPC-Gateway project.
	ProtoEndpointBinding http = 1190;

And the field names look very similar.

Supporting google.api.HttpRule would mean an existing application can more easily migrate to grpc-api-gateway for unary-unary RPCs, or use its protoc-gen-openapiv3 in conjunction with another request transcoder.

Though, this wouldn’t work for streaming RPCs.

[peymanmortazavi]

Ah I like that idea very much, they do map very easily actually. If you wanted to use the query parameter configurations new to this project, you would have to switch but for backwards compatibility, like you mentioned, that's a great idea!

Let's keep this ticket open to track that.