fix: Update OpenAPIServiceConnector to new ChatMessage

[vblagoje]

Why:

Update OpenAPIServiceConnector to handle new ChatMessage format

• fixes OpenAPIServiceConnector does not support the v2.9.x ChatMessage structure #8774

What:

• Patched the request method in OpenAPI to handle raw responses more effectively.
• Reworked the processing of chat messages to extract tool calls and handle them for OpenAPI function invocations.

How can it be used:

The changes affect how OpenAPIServiceConnector handles new ChatMessage format involving build in tool_calls property.

Example usage:

connector.run(messages=[message], service_openapi_spec=a_spec_as_a_dict_object)

Where message should now contain tool_calls property.

How did you test it:

Tests verify new behavior of message processing with checks for valid tool calls. Patched OpenAPI methods are mocked to assess correct invocation and response handling. Integration tests are skipped unless specific API keys are set.

Notes for the reviewer:

Pay special attention to the new patch applied to the request method of OpenAPI, specifically concerning raw response handling. Ensure the test coverage is sufficient for edge cases in tool call processing and response verification.

[coveralls]

Pull Request Test Coverage Report for Build 13162113609

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.

• For more information on this, see Tracking coverage changes with pull request builds.
• To avoid this issue with future PRs, see these Recommended CI Configurations.
• For a quick fix, rebase this PR at GitHub. Your next report should be accurate.

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 61 unchanged lines in 3 files lost coverage.
• Overall coverage decreased (-0.5%) to 90.814%

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Files with Coverage Reduction	New Missed Lines	%
components/embedders/sentence_transformers_document_embedder.py	2	96.77%
components/embedders/sentence_transformers_text_embedder.py	2	96.3%
components/connectors/openapi_service.py	57	61.22%

Totals
Change from base Build 13141979385:	-0.5%
Covered Lines:	8947
Relevant Lines:	9852

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💛 - Coveralls

[vblagoje]

@richardpaulhudson would you please give this branch a spin in your project by directly installing it via pip install git+https://github.com/deepset-ai/haystack.git@open_api_chat_message