Use class hierarchy to organize AgentChat message types and introduce StructuredMessage type

[ekzhu]

This PR refactored AgentEvent and ChatMessage union types to abstract base classes. This allows for user-defined message types that subclass one of the base classes to be used in AgentChat.

To support a unified interface for working with the messages, the base classes added abstract methods for:

• Convert content to string
• Convert content to a UserMessage for model client
• Convert content for rendering in console.
• Dump into a dictionary
• Load and create a new instance from a dictionary

This way, all agents such as AssistantAgent and SocietyOfMindAgent can utilize the unified interface to work with any built-in and user-defined message type.

This PR also introduces a new message type, StructuredMessage for AgentChat (Resolves #5131), which is a generic type that requires a user-specified content type.

You can create a StructuredMessage as follow:

class MessageType(BaseModel):
  data: str
  references: List[str]

message = StructuredMessage[MessageType](content=MessageType(data="data", references=["a", "b"]), source="user")

# message.content is of type `MessageType`. 

This PR addresses the receving side of this message type. To produce this message type from AssistantAgent, the work continue in #5934.

Added unit tests to verify this message type works with agents and teams.

[codecov]

Codecov Report

Attention: Patch coverage is 84.23237% with 38 lines in your changes missing coverage. Please review.

Project coverage is 76.89%. Comparing base (8a5ee3d) to head (6a1d51c).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
...utogen-agentchat/src/autogen_agentchat/messages.py	86.13%	19 Missing ⚠️
...togen_ext/agents/openai/_openai_assistant_agent.py	63.15%	7 Missing ⚠️
...gen-agentchat/src/autogen_agentchat/ui/_console.py	33.33%	6 Missing ⚠️
...entchat/teams/_group_chat/_chat_agent_container.py	91.30%	2 Missing ⚠️
...en_agentchat/teams/_group_chat/_base_group_chat.py	92.30%	1 Missing ⚠️
...en-agentchat/src/autogen_agentchat/utils/_utils.py	80.00%	1 Missing ⚠️
...perimental/task_centric_memory/utils/apprentice.py	50.00%	1 Missing ⚠️
...es/autogen-ext/src/autogen_ext/ui/_rich_console.py	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #5998      +/-   ##
==========================================
+ Coverage   76.78%   76.89%   +0.11%     
==========================================
  Files         191      191              
  Lines       13252    13358     +106     
==========================================
+ Hits        10175    10272      +97     
- Misses       3077     3086       +9     

Flag	Coverage Δ
unittests	76.89% <84.23%> (+0.11%)	⬆️

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[ekzhu]

Pausing the work here. Let's wait for more clarity from #4623 and consider structured message as part of that later.

First let's just focus on #5934 and use TextMessage with JSON string as the content.

[afourney]

In generally I like this PR.

I worry a little about the really long method names like content_to_model_message... but at least it's clear.

I'm also not sure about content_to_render. Doesn't this really depend on the media type or shell environment? E.g., I got hit on markitdown when people's shells were set to the charset gbk. Is there a better name for this?

[ekzhu]

I'm also not sure about content_to_render. Doesn't this really depend on the media type or shell environment? E.g., I got hit on markitdown when people's shells were set to the charset gbk. Is there a better name for this?

I changed it to content_to_text.... perhaps there can be some decoding parameters?

[ekzhu]

@jackgerrits @victordibia @afourney I made the change we have discussed so the type hints won't change, just replaced union with base class.

misclick