[nidhiii-27]

Adds mapping logic to classify exceptions, gRPC status codes, and HTTP response codes into standard OpenTelemetry error types.

• Adds StorageErrorTypeMapper for error.type classification across gRPC, GAX, HTTP, auth, checksum, and client network/timeout exceptions.
• Adds comprehensive unit tests in StorageErrorTypeMapperTest.

[gemini-code-assist]

Code Review

This pull request introduces comprehensive support for OpenTelemetry client metrics and debug metrics in Google Cloud Storage, including configuration options in StorageOptions, GrpcStorageOptions, and HttpStorageOptions. It adds utility classes such as StorageClientMetrics for instrument registration, StorageErrorTypeMapper for mapping exceptions to canonical error strings, StorageMetricsConfig for environment-based configuration, and StorageMetricsContext for tracking metric state across boundaries, along with corresponding unit tests. Feedback on the changes suggests simplifying a redundant null check on a transient field in StorageOptions, defensively preventing infinite loops from self-causation in StorageErrorTypeMapper's exception unwrapping, and robustly checking for authentication exceptions by using full class names instead of simple names to correctly handle anonymous classes.

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java-storage/google-cloud-storage/src/main/java/com/google/cloud/storage/StorageOptions.java (262)

Since meterProvider is marked as transient, it will not be serialized and will always be null after deserialization. Therefore, the check this.meterProvider != null in readObject is redundant and will always evaluate to false. We can simplify this to only check this.customMeterProviderConfigured.

    if (this.customMeterProviderConfigured) {

java-storage/google-cloud-storage/src/main/java/com/google/cloud/storage/StorageErrorTypeMapper.java (159-162)

To prevent potential infinite loops in case of custom exceptions with self-causation (where t.getCause() == t), we should defensively add a check for t.getCause() != t in the while loop condition, similar to how it is handled at the end of the mapThrowable method.

    while ((t instanceof ExecutionException || t instanceof CompletionException)
        && t.getCause() != null
        && t.getCause() != t) {
      t = t.getCause();
    }

java-storage/google-cloud-storage/src/main/java/com/google/cloud/storage/StorageErrorTypeMapper.java (258)

Using t.getClass().getSimpleName() can return an empty string "" for anonymous classes, which would bypass the contains("Auth") check even if the base class name contains "Auth". Using the full class name className.contains("Auth") is more robust and avoids extra string parsing overhead.

    if (className.contains("Auth")) {