feat: Support Mongodb full text search

[alperkaya]

Related Issues

• fixes Full-text MongoDBAtlas Retriever #872

Proposed Changes:

It works in the same way as embedding retrieval works

How did you test it?

added new unit tests, and manual verification

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:.

[anakin87]

Hello and thanks for the contribution.
I will take a look in the next few days...

In the meantime:

• let's make sure that all the tests pass in the CI
• thoroughly test the feature locally
• be aware that tests in test_embedding_retrieval (requiring a cloud MongoDB instance) are skipped when running from a fork, for security reasons
• create a test_fulltext_retrieval file, similar to test_embedding_retrieval and containing integration tests (requiring a cloud MongoDB instance). They won't run in this PR but when everything else is fine, I will check them.

[alperkaya]

Hello and thanks for the contribution. I will take a look in the next few days...

In the meantime:

* let's make sure that all the tests pass in the CI

* thoroughly test the feature locally

* be aware that tests in test_embedding_retrieval (requiring a cloud MongoDB instance) are skipped when running from a fork, for security reasons

* create a test_fulltext_retrieval file, similar to [test_embedding_retrieval](https://github.com/deepset-ai/haystack-core-integrations/blob/f95dd06614ed3089fa1fe4a0ce780b52949dc8e3/integrations/mongodb_atlas/tests/test_embedding_retrieval.py) and containing integration tests (requiring a cloud MongoDB instance). They won't run in this PR but when everything else is fine, I will check them.

Hello,

I have simplified the production code by removing the filter functionality to make the review process easier and more straightforward. Once this change is approved, I can reintroduce the filter functionality. Additionally, I tested the implementation using a connection to Atlas DB and included the sample data I used in the test code.