classification of "trailers-only" responses for gRPC and gRPC-Web is not quite right #268
Description
The logic in the client looks for a "grpc-status" key in response headers to decide if the response is a "trailers-only" response. But the gRPC spec classifies this more rigorously as a headers frame that terminates the HTTP/2 stream. Expanding this to HTTP 1.1, it would be a response that has headers but no response body and no trailers. The current mechanism would misinterpret a response as "trailers-only" if it had an erroneous "grpc-status" header key, even if the response had both a response body and subsequent trailers. To be more compliant with the spec, this client should only consider a response to be "trailers-only" when it observes the end of the response and there was no body and were no trailers. Only then should it query for a "grpc-status" key from the headers.