Add gRPC Server Reflection support

[jchadwick-buf]

Is your feature request related to a problem? Please describe. gRPC and connect-go support a server-side reflection API that serves protobuf schema information to clients. As of now, connect-node does not support this feature.

This feature would be useful as various gRPC debugging utilities can use it to grab schema information on-demand.

Describe the solution you'd like Ideally, connect-node would have an optional implementation of serverside reflection, including the necessary code generation in protobuf-es to support this (as needed.)

Additional context gRPC Server Reflection Protocol connect-go grpcreflect implementation

[tantona]

This would be super handy! I'm commenting here in the hopes that it helps get it on the roadmap! :)

[nicocossiom]

+1 on this one, let's hope we get some more feature parity between the Node and Go ConnectRPC libraries. Still very happy with the current Node implementation, this would just make it more complete. Thank you to the contributors and the ConnectRPC team as a whole.

[stevenceuppens]

+1 this would greatly improve integration into things like postman etc... which many of our dev use on their current REST apis.

There is a reference implementation available on the https://github.com/grpc/grpc-node project https://www.npmjs.com/package/@grpc/reflection