split method in ServerCallContext to service and method

Now if you try access to method name from context you will see only full name and no way to get access separately to Name and ServiceceName fields, only through access private filed _method (part of JsonTranscodingServerCallContext)
https://github.com/dotnet/aspnetcore/blob/98c4546ddccfe2f62c4dc239fabd0c92848b255d/src/Grpc/JsonTranscoding/src/Microsoft.AspNetCore.Grpc.JsonTranscoding/Internal/JsonTranscodingServerCallContext.cs#L23

Is it possible to make _method public?

Read src/Grpc/JsonTranscoding/src/Microsoft.AspNetCore.Grpc.JsonTranscoding/Internal/JsonTranscodingServerCallContext.cs at the referenced _method field, then inspect how ServerCallContext exposes method information. Done means callers can access the service and method names separately through a supported API rather than the private field.

Written by the indexing model from the issue text.