chore: Update 1.0-dev branch

[lkawka]

No description provided.

[gemini-code-assist]

Summary of Changes

Hello @lkawka, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request significantly enhances the A2A client's flexibility and reliability by introducing dynamic version control for the A2A specification generation script, allowing developers to target specific versions of the schema. It also expands the client's messaging capabilities by enabling the attachment of arbitrary metadata to requests, which is crucial for extensibility. Furthermore, the changes refine the internal protobuf utility functions to ensure proper handling of message and artifact extensions, supported by new test cases to validate the metadata flow.

Highlights

• Flexible A2A Specification Versioning: The generate_types.sh script now supports specifying the A2A specification version via a command-line flag (--version) or an environment variable (A2A_SPEC_VERSION), allowing dynamic fetching of the schema from GitHub based on git tags, branches, or commit SHAs.
• Request Metadata Support in Client: The send_message methods in base_client.py and client.py have been extended to accept an optional request_metadata dictionary, enabling the inclusion of additional context or extensions with outgoing messages.
• Improved Protobuf Serialization for Extensions: The proto_utils.py module has been updated to correctly handle extensions fields when converting between internal Message and Artifact types and their protobuf representations.
• Enhanced Script Robustness and Validation: The generate_types.sh script now includes validation for local input file existence and remote URL accessibility, providing clearer error messages if the specified A2A specification version cannot be found.
• Client Test Coverage for Metadata: New tests have been added to test_base_client.py to ensure that the request_metadata parameter is correctly propagated and passed to the underlying transport layer during message sending.

Ignored Files

• Ignored by pattern: .github/workflows/** (4)
  • .github/workflows/linter.yaml
  • .github/workflows/python-publish.yml
  • .github/workflows/unit-tests.yml
  • .github/workflows/update-a2a-types.yml
• Ignored by pattern: CHANGELOG.md (1)
  • CHANGELOG.md

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[gemini-code-assist]

Code Review

This pull request introduces several enhancements. The generate_types.sh script is significantly improved to allow specifying the A2A specification version via an environment variable or a command-line flag, with support for tags, branches, and commit SHAs. It also adds URL validation and better error messages. The client-side code is updated to support passing request_metadata when sending messages, and proto_utils is updated to handle extensions in Message and Artifact types. The changes are well-tested. My feedback includes a minor suggestion to improve the robustness of the shell script.

[gemini-code-assist]

Git commit SHAs are case-insensitive, though they are usually represented in lowercase. It would be more robust to allow uppercase hex characters in the regex to handle SHAs that might contain them.

Suggested change

	elif [[ "$version" =~ ^[0-9a-f]{7,40}$ ]]; then
	elif [[ "$version" =~ ^[0-9a-fA-F]{7,40}$ ]]; then