feat: add a2a server and client plugins and samples

[lilyydu]

• completed a2a client plugin
• completed a2a server plugin
• completed a2a server + client sample test

NOTE #1: Due to the event looping implementation by the external a2a SDK, they may raise a CancelledError when in debug mode. This is because EventConsumer.consume_all will attempt to dequeue the event, with a 0.5 second timeout.
Our response however takes more than 0.5 seconds to generate.
Hence, the task is cancelled by wait_for, which causes CancelledError.
This is raised by the coroutine DefaultRequestHandler, but consume_all recognizes it as TimeoutError and will continue to reloop and try again. I don't think there is any way to mitigate this as our response takes ~ 1 second to generate.

NOTE #2: Improving the event type hinting will be a separate WI, for now I am using a specific key. This feels like a larger ticket b/c I think we should improve our typing hints for all our events in general. I noticed we can do the following (string or any type versus ErrorEvent) & it doesn't complain-

@app.event("error")
async def handle_error(event: str) -> None:

NOTE #3: Will follow with docs soon after.

Sample example:

[Copilot]

Pull Request Overview

This PR introduces comprehensive support for Agent-to-Agent (A2A) protocol communication in the Microsoft Teams AI Library, enabling agents to communicate with each other using the A2A SDK. The implementation includes both server and client capabilities with a complete test application demonstrating bidirectional agent communication.

Key Changes:

• Implemented A2A server plugin (A2APlugin) for exposing agents via A2A protocol
• Implemented A2A client plugin (A2AClientPlugin) for consuming A2A agents
• Added comprehensive test application demonstrating both server and client functionality
• Modified event registration to log warnings instead of raising errors for unregistered event types

Reviewed Changes

Copilot reviewed 16 out of 17 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
tests/a2a-test/src/main.py	Complete test application demonstrating A2A server and client integration with weather agent example
tests/a2a-test/pyproject.toml	Project configuration for a2a test application with required dependencies
tests/a2a-test/README.md	Documentation explaining the test application usage with example conversations
packages/apps/src/microsoft/teams/apps/app.py	Changed unregistered event type handling from error to info log
packages/a2aprotocol/src/microsoft/teams/a2a/server/plugin.py	A2A server plugin implementation with middleware support and FastAPI integration
packages/a2aprotocol/src/microsoft/teams/a2a/server/logging_middleware.py	Logging middleware for A2A server requests
packages/a2aprotocol/src/microsoft/teams/a2a/server/custom_agent_executor.py	Custom agent executor implementing A2A message handling with event emission
packages/a2aprotocol/src/microsoft/teams/a2a/server/a2a_plugin_options.py	Configuration options for A2A server plugin
packages/a2aprotocol/src/microsoft/teams/a2a/server/init.py	Server module exports
packages/a2aprotocol/src/microsoft/teams/a2a/chat_prompt/types.py	Type definitions for A2A client plugin including metadata builders and configuration
packages/a2aprotocol/src/microsoft/teams/a2a/chat_prompt/plugin.py	A2A client plugin implementation with agent card fetching and function registration
packages/a2aprotocol/src/microsoft/teams/a2a/chat_prompt/agent_config.py	Agent configuration model for storing client connection details
packages/a2aprotocol/src/microsoft/teams/a2a/chat_prompt/agent_client_info.py	Model combining agent config with client instance and card
packages/a2aprotocol/src/microsoft/teams/a2a/chat_prompt/init.py	Client module exports
packages/a2aprotocol/src/microsoft/teams/a2a/init.py	Root module exports combining server and client functionality
packages/a2aprotocol/pyproject.toml	Updated package name and added AI/apps dependencies

Comments suppressed due to low confidence (1)

packages/a2aprotocol/src/microsoft/teams/a2a/chat_prompt/types.py:18

• Missing docstring for the FunctionMetadata class. As this is a public API type, it should include a class docstring explaining its purpose in the A2A context.

class FunctionMetadata(BaseModel):
    name: str
    description: str

[heyitsaamir]

Nice this is looking solid!