How to enable support of the reflection API

[dchebakov]

Hi, thank you for the awesome library!

I have used grpcurl cli to inspect my dev grpc server (run by python manage.py grpcrunserver --dev) and then trying to inspect available methods using grpcurl -plaintext localhost:50051 list:

$ grpcurl -plaintext localhost:50051 list
Failed to list services: server does not support the reflection API

I would like to know is there a way to enable reflection api? I think it would be useful to inspect new apis for the documentation purpose like openapi or something