gRPC Transcoding: options to ser/deserialize enums without prefix

[alrz]

Is there an existing issue for this?

• I have searched the existing issues

Is your feature request related to a problem? Please describe the problem.

Since C# protogen already drops the prefix I think transcoding endpoint should be able to do that as well, perhaps with an opt-in option.

Describe the solution you'd like

Right now there's an option to serialize enums as integer.

I propose to add another option to write enums as string (the default) but without a prefix however this should still keep it as UPPERCASE.
On the deserialization, for the maximum compatibility it should accept the name without prefix in addition to the exact match.
There's also a question about case-sensitivity on deserialization and whether or not it should be configurable.

Additional context

Due to incompatibility between proto convention through transcoding and graphql schema, we're forced to match either side to the other and since protocolbuffers/protobuf#4328 is not available at the moment I think the dotnet impl could be relaxed to cover this.

The alternative is allowing custom converters filed at #46712