feat: add revision parameter to Sentence Transformers embedder components

[swapniel99]

Related Issues

None

Proposed Changes:

Added a revision parameter to all Sentence Transformers embedder components to allow users to specify a specific model revision/version from the Hugging Face Hub. This parameter is passed through to the underlying Sentence Transformers backend.

How did you test it?

• Added unit tests for all four embedder components to verify the revision parameter is correctly:
  • Initialized with default value (None)
  • Set when provided explicitly (e.g., "v1.0")
  • Serialized and deserialized in to_dict() and from_dict() methods
• Updated existing backend initialization tests to include the revision parameter
• All pre-commit hooks passed successfully

Notes for the reviewer

The revision parameter follows the same pattern as other optional parameters like trust_remote_code and local_files_only. It's passed directly to the Sentence Transformers model initialization, allowing users to pin to specific model versions for reproducibility.

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

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[coveralls]

Pull Request Test Coverage Report for Build 19096477217

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.
• 31 unchanged lines in 6 files lost coverage.
• Overall coverage increased (+0.006%) to 92.25%

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Files with Coverage Reduction	New Missed Lines	%
components/embedders/sentence_transformers_sparse_document_embedder.py	1	98.41%
components/embedders/sentence_transformers_sparse_text_embedder.py	1	98.08%
components/embedders/sentence_transformers_document_embedder.py	2	97.01%
components/embedders/sentence_transformers_text_embedder.py	2	96.49%
components/agents/agent.py	9	96.48%
utils/base_serialization.py	16	87.6%

Totals
Change from base Build 18976263337:	0.006%
Covered Lines:	13511
Relevant Lines:	14646

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💛 - Coveralls

[sjrl]

@swapniel99 could you also add a release note following our guidelines here and fix the failing linting errors. You can reproduce this locally by running hatch run test:lint haystack. Also explained in our contributions guidelines here

[sjrl]

Thanks for the addition!

[swapniel99]

@swapniel99 could you also add a release note following our guidelines here and fix the failing linting errors. You can reproduce this locally by running hatch run test:lint haystack. Also explained in our contributions guidelines here

I checked but these lines were not edited by me. I don't understand what is supposed to be done here.
Running the lint check is extremely slow on my laptop.