Maybe add overload of providing ExtensionRegistryLite to Marhsallers #1678
Description
Somehow, some way, extension registries need to be passable to the grpc unmarshalling code. Right now there isn't a good way to do so, due to marshalling being directly referenced by the stub, rather than the server/channel. This means any code that is using proto2 extensions won't work with grpc. Some ideas:
- Make the stub code accept an extension registry if the proto syntax that generated the file is proto2
- Allow a way for the extension registry to be passed to the client or server
- Something else.