Ensure that gRPC Java implementation conforms to standard status codes in gRPC

[hsaliak]

Error code specification - https://github.com/grpc/grpc/blob/master/doc/statuscodes.md

[thefallentree]

We were seeing some INTERNAL error codes

[ejona86]

@thefallentree please create a new issue with the error information so that we have something actionable to go on. Note that as far as this issue is concerned, INTERNAL error codes are allowed.

[nmittler]

After code inspection, everything seems correct except for the cases below:

Case	Expected	gRPC-Java
Compression mechanism used by client not supported at server	UNIMPLEMENTED	INTERNAL
Server temporarily out of resources (e.g., Flow-control resource limits reached)	RESOURCE_EXHAUSTED	NA

Status codes that should not be used:

Code	Usage
INVALID_ARGUMENT	Marshalling JSON, Server receives multiple messages for UNARY, Half-closing server stream without a request

[nmittler]

@hsaliak @ejona86 audit is done ... next step is to determine what (if any) issues to create to address the discrepancies.

[ejona86]

UNIMPLEMENTED in wrong in the spec; that is not appropriate. We need to have a conversation to fix the spec. JSON failure should swap to INTERNAL. We need a discussion for problems with unary calls.

[ejona86]

After lengthy discussion, UNIMPLEMENTED is going to stay in the spec for unknown compression type.