impl: gRPC server logging interceptors

[anj-s]

Summary

• gRPC Server Logging Interceptors: Implemented and registered logging interceptors for both unary and stream gRPC services in the AX server.
• Unary Interceptor (LoggingInterceptor): Captures and logs incoming unary RPC details, including full method names, duration, request success/failure, and dynamically extracts and includes conversation_id in log context if the request supports GetConversationId().
• Stream Interceptor (StreamLoggingInterceptor): Logs stream lifecycle events (start, complete, fail) along with latency, method names, and errors.
• Service Integration: Registered the logging interceptors in both the standard server (server.go) and the harness server (server_harness.go) using grpc.ChainUnaryInterceptor and grpc.ChainStreamInterceptor.
• Unit Testing: Added a robust mock-server test suite using bufconn to assert correct log formats, message contents, and error handling for both successful and failing unary/stream calls.

Type of Change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Refactor (cleanups and structured logging migration)
• Documentation
• Breaking change (fix or feature that would cause existing functionality to not work as expected)

Related Issues

Part 2 of the Observability & Monitoring epic.

Test Plan

• Automated Tests: Unit tests pass for both standard and harness build tags:

  go test -v ./internal/server
  go test -v -tags harness ./internal/server

• Verification: Verified correct log output structures and assert JSON format validation (e.g. conversation_id propagation).

Notes for Reviewer

This is the second of 5 planned modular PRs to roll out comprehensive AX observability. It introduces automatic logging for gRPC server entrypoints.