Add top_k for create_chat and update_chat api

[Feiue]

What problem does this PR solve?

Add top_k for create_chat and update_chat api #4157

Type of change

• New Feature (non-breaking change which adds functionality)

[panzi]

Great!

It doesn't seem to be returned with the Chat.Prompt object, though:

Error: 'Base' object has no attribute 'top_k'
Traceback (most recent call last):
  File "/app/src/ai/index_manager.py", line 701, in create_ragflow_store
    assistant.prompt.top_k != RAGFLOW_TOP_K:
    ^^^^^^^^^^^^^^^^^^^^^^
AttributeError: 'Base' object has no attribute 'top_k'

I guess that's a separate bug/feature request.

[panzi]

New issue: #4886

[KevinHuSh]

I don't get it.