feat: integrate A2A x402 plugin with reference implementation from google-agentic-commerce/a2a-x402

[gitctrlx]

Objective

Integrate the A2A x402 plugin into this project, following the reference implementation provided in google-agentic-commerce/a2a-x402.

Scope

• Review the architecture and plugin interfaces of qntx/ra2a
• Analyze and reuse relevant modules from the reference implementation
• Ensure compatibility and extensibility

Implementation Plan

1. Study the a2a-x402 repository and its plugin integration workflow
2. Design integration points for the plugin within qntx/ra2a
3. Develop abstraction and adaptation layers if needed
4. Implement the integration, following best practices for maintainability
5. Add thorough documentation and usage examples

Acceptance Criteria

• Successful plugin integration with working examples
• All tests passing
• Documentation updated

References

• google-agentic-commerce/a2a-x402