fix: validate grpc-accept-encoding header when client sends gzip request

[jlaportebot]

Summary

This PR implements validation for the grpc-accept-encoding response header when the client sends a gzip-encoded request.

According to the gRPC spec, when a client sends a gzip-encoded request, the server must respond with grpc-accept-encoding: gzip in the response headers to indicate it can accept gzip-encoded responses. If this header is missing or doesn't include gzip, it's a server misbehavior.

Changes

1. Added validation logic in Http2ClientStreamTransportState.transportHeadersReceived() that:

   • Tracks when the client sends a gzip-encoded request via setMessageCompression(boolean, String)
   • Validates the server's grpc-accept-encoding header when client sent gzip
   • Logs a warning at FINE level if the header is missing or doesn't include gzip

2. Extended ClientStream interface with setMessageCompression(boolean enabled, String compressorName) method to pass compressor information to the transport layer

3. Updated all ClientStream implementations to support the new method signature:

   • AbstractClientStream.TransportState (base implementation)
   • Http2ClientStreamTransportState (actual validation logic)
   • ForwardingClientStream, NoopClientStream, DelayedStream, RetriableStream
   • InProcessTransport (both client and server streams)
   • MultiMessageClientStream, SingleMessageClientStream (binder transport)

4. Added comprehensive unit tests in Http2ClientStreamTransportStateGrpcAcceptEncodingTest.java covering:

   • Valid grpc-accept-encoding: gzip header
   • Missing header when gzip was sent (logs warning)
   • Header with only identity when gzip was sent (logs warning)
   • Header with gzip,deflate when gzip was sent (OK)
   • No client compression (no validation needed)
   • Case-insensitive header value matching (GZIP, gzip)

Testing

All existing tests pass. New tests added for the validation logic.

Fixes #1804

[linux-foundation-easycla]

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