Summary

This PR adds serde aliases to GcsConfig fields to support multiple configuration key naming conventions, enabling seamless migration from Arrow object_store and other file system libraries. Users can now use either OpenDAL's native field names or Google-prefixed alternatives.

Changes

Added #[serde(alias = "...")] attributes to 5 key GCS configuration fields, following the exact same patterns used by Apache Arrow's object_store library.

Example Usage

// Original OpenDAL style (still works)
{
  "bucket": "my-bucket",
  "service_account": "/path/to/sa.json",
  "credential": "service-account-key-json"
}

// Google SDK style (now supported!)
{
  "google_bucket": "my-bucket", 
  "google_service_account": "/path/to/sa.json",
  "google_service_account_key": "service-account-key-json"
}

Added Aliases

Missing Configurations (Future Work)

These Arrow object_store configurations are not yet available in OpenDAL and could be added in future PRs:

HTTP Client Configuration

Notes on Missing Configurations

• HTTP Client Options: OpenDAL's GCS service doesn't currently expose low-level HTTP client configurations. These could be valuable for users who need fine-grained control over connection behavior, timeouts, and proxy settings.
• Proxy Support: While OpenDAL may have global proxy support, GCS-specific proxy configuration aliases are not available.
• HTTP Version Control: Arrow object_store allows forcing HTTP/1 or HTTP/2, which could be useful for compatibility with different GCS endpoints.

Testing

• ✅ Added comprehensive unit tests covering all aliases
• ✅ All existing GCS tests pass
• ✅ Code compiles without warnings
• ✅ Clippy passes without issues

Backward Compatibility

This change is fully backward compatible. All existing configurations continue to work exactly as before, with the new aliases providing additional flexibility.

Similar to #6524