feat: Add outputs_to_string to Tool and ComponentTool

[sjrl]

Related Issues

• fixes State and Tool proposed Changes from feedback haystack-experimental#237

Proposed Changes:

Adds outputs_to_string to Tool and ComponentTool to allow users to customize how the output of a Tool should be converted into a string so that it can be provided back to the ChatGenerator in a ChatMessage.

If outputs_to_string is not provided a default converter is used within ToolInvoker. The default handler uses the current default behavior.

How did you test it?

Updated tests.

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

[coveralls]

Pull Request Test Coverage Report for Build 14193875653

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 27 unchanged lines in 3 files lost coverage.
• Overall coverage decreased (-0.09%) to 90.004%

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Files with Coverage Reduction	New Missed Lines	%
tools/tool.py	6	93.68%
tools/component_tool.py	10	93.67%
components/tools/tool_invoker.py	11	90.3%

Totals
Change from base Build 14192152242:	-0.09%
Covered Lines:	10282
Relevant Lines:	11424

---

💛 - Coveralls

[anakin87]

I had an initial look...
Please fix the mypy errors

[anakin87]

I think there is room for future improvements for everything related to Agent.

However, this PR is good to go.

[sjrl]

I think there is room for future improvements for everything related to Agent.

However, this PR is good to go.

@anakin87 what ideas do you have for future improvements?