AutoGen Studio: Serve responding complete messages

[mariohmol]

Why are these changes needed?

Run the Studio with serve:
autogenstudio serve --team notebooks/team.json --port 8084

Open the doc endpoint (http://127.0.0.1:8084/docs) and make a request, you will notice the response does not show content for messages.

With this fix you will see full payload:

This error might be something related to FastAPI vs pydantic, as we are using some "complex" model structuring .
TaskResult -> BaseChatMessage(BaseMessage, ABC) -> BaseTextChatMessage(BaseChatMessage, ABC) -> TextMessage(BaseTextChatMessage)

Probably the serializer use its parent to serialize, and then can't access extension attributes declared by children classes.

PS: We have /docs page with the available endpoints, but it is not mentioned on our documentation or we could show on the Studio Deploy view. Seems that the documentation is out of date as many times it says --workflow but now is --team

Related issue number

Opened a discussion on discord.

Checks

• [ X ] I've included any doc changes needed for https://microsoft.github.io/autogen/. See https://github.com/microsoft/autogen/blob/main/CONTRIBUTING.md to build and test documentation locally.
  ** As this is more like a bug, I believe doc change is not needed, as is expected to see full LLM results **

• [ X ] I've added tests (if relevant) corresponding to the changes introduced in this PR.

• [ ] I've made sure all auto checks have passed.
  ** Checkin **

[mariohmol]

@microsoft-github-policy-service agree

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 79.69%. Comparing base (9065c6f) to head (469de84).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #6520   +/-   ##
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  Coverage   79.69%   79.69%           
=======================================
  Files         228      228           
  Lines       17025    17025           
=======================================
  Hits        13568    13568           
  Misses       3457     3457           

Flag	Coverage Δ
unittests	79.69% <ø> (ø)

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