Consider to register the "Content-Type" to IANA

[bogdandrutu]

I found that iana allows registration for custom mime types https://www.iana.org/assignments/media-types/media-types.xhtml#application, should gRPC register their types there?

From https://github.com/grpc/grpc/blob/master/doc/PROTOCOL-HTTP2.md#requests this should be "application/grpc", "application/grpc-protobuf", etc.

[davinkevin]

+1 and maybe an entry in the IANA database for protocol and port. With it, we could rely on this list in k8s services, using the appProtocol field.