Streaming responses

[axelsrz]

This pull request introduces several enhancements and new features across multiple modules, focusing on streaming capabilities, AI-generated content handling, and citation utilities. The most significant changes include the addition of a streaming_response property to the turn context, support for AI entities in activities, and utility functions for citation management.

Streaming Enhancements:

• Added a streaming_response property to TurnContext in libraries/Builder/microsoft-agents-builder/microsoft/agents/builder/turn_context.py, enabling partial response streaming to clients.
• Introduced StreamingResponse, StreamingChannelData, and related classes in libraries/Hosting/microsoft-agents-hosting-aiohttp/microsoft/agents/hosting/aiohttp/app/streaming, providing foundational support for streaming operations. [1] [2]

AI-Generated Content:

• Added AIEntity and related models in libraries/Core/microsoft-agents-core/microsoft/agents/core/models/ai_entity.py to represent AI-generated content and citations. Also included a utility function, add_ai_to_activity, for associating AI entities with activities.
• Updated Activity class in libraries/Core/microsoft-agents-core/microsoft/agents/core/models/activity.py to support AI entities using SerializeAsAny.

Citation Utilities:

• Introduced CitationUtil in libraries/Hosting/microsoft-agents-hosting-aiohttp/microsoft/agents/hosting/aiohttp/app/streaming/citation_util.py, providing methods for formatting citation responses, clipping text, and extracting used citations from text.

Miscellaneous Improvements:

• Enhanced model_dump in ConnectorClient to exclude None values when replying to activities, optimizing payloads.
• Updated __init__.py files across modules to export new classes and utilities for broader accessibility. [1] [2] [3]

[rido-min]

LGTM

[tracyboehrer]

The only other consideration is the DotNet AgentApplication will call EndStream if needed. More of a request from Teams to ensure it's called even in the event of an exception.