`grpc-kafka` feature (enhanced)

[jfallows]

Enhanced

• binding-grpc assumes http network mapping to grpc application streams
  • [ ] integrate guard for authorization via authorization request metadata (delegate to http instead?)
  • [ ] enforce validation of rpc inbound .proto definition message types (required fields, field types, etc)
    • see protoc-gen-validate
  • [ ] https://github.com/aklivity/zilla/issues/955
  • [ ] support non-identity content compression; gzip, deflate, snappy
  • [ ] https://github.com/aklivity/zilla/issues/954
• binding-grpc-kafka maps grpc streams to kafka streams
  • [ ] unreliable client streaming, similar to oneway produce, without streaming idempotency keys and acks
  • [ ] reliable client streaming, similar to oneway produce, with streaming idempotency keys and acks
  • [ ] support converting inbound messages to json or schema typed payload, potentially streamed
  • [ ] support converting outbound messages from json or schema typed payload, potentially streamed
• binding-kafka-grpc maps kafka streams to grpc streams
  • [ ] resilient retry with progressive backoff when grpc server unavailable
  • [ ] unreliable client streaming, similar to oneway produce, without streaming idempotency keys and acks
  • [ ] unreliable server streaming, similar to sse-kafka without last-event-id
  • [ ] reliable client streaming with idempotency keys and acks (similar to webhook, but streaming)
  • [ ] reliable server streaming, similar to sse-kafka with last-event-id
• binding-rest-grpc maps rest APIs to grpc services
  • [ ] convert REST json to and from grpc protobuf message structures

[dudo]

I just ran into the missing reflection. I was trying to validate the server is receiving requests

> grpcurl -plaintext localhost:9090 list                                                                                                                                               
Failed to list services: rpc error: code = Unknown desc = malformed header: missing HTTP content-type

That might be a nice one to start with.