[#753] Add Support for CopilotStudio Agent-to-Agent Connector for AgentsSDK to populate UserAuthorization

[ceciliaavila]

Fixes #753

Description

This PR adds the new MCSConnectorClient and the ConnectorUserAuthorization handler to support the Copilot Studio Agent-to-Agent feature.

Detailed Changes

• Added new ConnectorUser role type.
• Added new ConnectorClientBase interface, which is implemented by the two connector client types.
• Added the new MCSConnectorClient class, which implements only two methods: replyToActivity and sendToConversation.
• Updated ConnectorClient to implement the ConnectorClientBase interface.
• Added new ConnectorUserAuthorization handler and related interfaces.
• Updated AuthorizationManager to instantiate the new ConnectorUserAuthorization handler.
• Updated CloudAdapter including a new createConnectorClientBase function which will decide, based on the activity.recipient.role, which connectorClient to create.
• Added test-agents/copilotstudio-agent-connector sample to showcase the new feature.

Testing

As the A2A feature is not yet available in Copilot Studio, we tested the implementation and the sample by mocking an activity with role 'connectoruser'. The token retrieval logic couldn't be tested.

These images show the code executed during this test.