feat: Update streaming chunk

[sjrl]

Related Issues

• fixes Extend StreamingChunk to have tool_calls, tool_results, finish_reason, usage #9358

Proposed Changes:

Updated StreamingChunk to add the fields tool_call, tool_call_result, index, and start to make it easier to format the stream in a streaming callback.

• Added new dataclass ToolCallDelta for the StreamingChunk.tool_call field to reflect that the arguments are a string delta rather than a Dict
• Updated print_streaming_chunk utility method to use these new fields. This especially improves the formatting when using this with Agent.
• Updated OpenAIChatGenerator and HuggingFaceAPIChatGenerator to follow the new dataclass.
• Updated ToolInvoker to follow the new format and also it now returns a final StreamingChunk that contains finish_reason="tool_call_result" in its metadata.

How did you test it?

• TODO add more unit tests

• Tested Agent streaming locally with OpenAIChatGenerator

Before Changes

After Changes

• Notable differences
  • Possible to add the [ASSISTANT] header
  • Easier to have better spacing between sections (e.g. between two tool calls)

Notes for the reviewer

Checklist

• I have read the contributors guidelines and the code of conduct
• I have updated the related issue with new insights and changes
• I added unit tests and updated the docstrings
• I've used one of the conventional commit types for my PR title: fix:, feat:, build:, chore:, ci:, docs:, style:, refactor:, perf:, test: and added ! in case the PR includes breaking changes.
• I documented my code
• I ran pre-commit hooks and fixed any issue

[sjrl]

I thought about making

content = Union[str, ToolCallDelta, ToolCallResult]

but this would be a breaking change b/c users expect content to always be a string. And this breaks StreamingChunk to ChatMessage implementations (mostly in private methods).

[coveralls]

Pull Request Test Coverage Report for Build 15191185377

Warning: This coverage report may be inaccurate.

This pull request's base commit is no longer the HEAD commit of its target branch. This means it includes changes from outside the original pull request, including, potentially, unrelated coverage changes.

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Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 63 unchanged lines in 9 files lost coverage.
• Overall coverage decreased (-0.07%) to 90.342%

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Files with Coverage Reduction	New Missed Lines	%
components/builders/answer_builder.py	1	98.53%
dataclasses/init.py	1	46.15%
core/super_component/super_component.py	4	95.83%
components/generators/chat/hugging_face_api.py	6	93.88%
dataclasses/streaming_chunk.py	6	84.62%
components/generators/chat/openai.py	9	95.36%
components/tools/tool_invoker.py	9	83.67%
components/generators/utils.py	11	10.53%
core/super_component/utils.py	16	86.61%

Totals
Change from base Build 15182795258:	-0.07%
Covered Lines:	11169
Relevant Lines:	12363

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💛 - Coveralls

[tstadel]

Looks very good to me already. 👍