test(showcase): Add gRPC and HttpJson Showcase ITs to verify Error Details

[nnicolee]

Description

This PR introduces E2E integration test coverage for standard and custom error details using the FailEchoWithDetails RPC in Showcase, validating the exception propagation and deserialization pipeline across both gRPC and HTTP/JSON transports.

Key Changes

• gRPC Transport Verification:
  • Verifies unpacking and correctness of all 10 standard error details (e.g. ErrorInfo, RetryInfo, DebugInfo, QuotaFailure, PreconditionFailure, BadRequest, RequestInfo, ResourceInfo, Help, LocalizedMessage).
  • Verifies that Showcase-specific custom trailers (e.g. PoetryError) are successfully unpacked and mapped into the client-side ErrorDetails.
  • Verifies dynamic message propagation inside custom trailers when parameters are passed to the request.
• HTTP/JSON Transport Verification:
  • Verifies that error status code mapping (e.g. ABORTED) propagates correctly.
  • Handles GAX's HTTP/JSON parser boundaries when dealing with unregistered custom types (like PoetryError) in JSON status payloads.

[gemini-code-assist]

Code Review

This pull request introduces a new integration test class, ITErrorDetails.java, to verify that standard and custom error details are correctly parsed and unpacked from ApiException for both gRPC and HTTP/JSON clients. The review feedback highlights two main areas for improvement: ensuring exception-safe resource cleanup in destroyClients() to prevent potential resource leaks if one of the clients fails to close, and avoiding the use of fully qualified class names when there are no naming conflicts to improve code readability.

[gemini-code-assist]

If grpcClient.close() throws an exception, httpjsonClient.close() will not be called, leading to a potential resource leak. To ensure both clients are closed and terminated properly, use nested try-finally blocks.

  static void destroyClients() throws InterruptedException {
    try {
      try {
        grpcClient.close();
      } finally {
        grpcClient.awaitTermination(TestClientInitializer.AWAIT_TERMINATION_SECONDS, TimeUnit.SECONDS);
      }
    } finally {
      try {
        httpjsonClient.close();
      } finally {
        httpjsonClient.awaitTermination(
            TestClientInitializer.AWAIT_TERMINATION_SECONDS, TimeUnit.SECONDS);
      }
    }
  }

References

1. When managing a collection of closeable resources (e.g., scopes), ensure they are closed in the reverse order of their creation (LIFO). The implementation must be exception-safe to prevent resource leaks, meaning all opened resources should be closed even if exceptions occur during their creation or closing.

[nnicolee]

Other existing integration tests uses this sequential pattern (such as ITIam.java, ITPagination.java, ITServerSideStreaming.java, etc.), we can leave this as-is to maintain consistency and readability.

[lqiu96]

Lint issue looks external:

[ERROR] Failed to execute goal com.spotify.fmt:fmt-maven-plugin:2.25:check (default-cli) on project grpc-google-cloud-sql-v1: Found 6 non-complying files, failing build -> [Help 1]
[ERROR] Failed to execute goal com.spotify.fmt:fmt-maven-plugin:2.25:check (default-cli) on project grpc-google-cloud-sql-v1beta4: Found 1 non-complying files, failing build -> [Help 1]

Hmm, maybe we try and update the branch. Maybe got fixed in main