feat: Add filter_policy to mongodb_atlas integration

[vblagoje]

Why:

Adds flexible filtering options to mongodb_atlas integration. By introducing a filter policy option (replace or merge), developers can now control how runtime filters are applied relative to initialization time filters.

• partially fixes Add filter_policy init parameter to all retrievers #780
• supersedes feat: Add filter_policy init parameter to all retrievers #781

What:

• Added filter_policy parameter with options replace and merge across multiple retrievers to control filter behavior dynamically.
• Unit tests were updated or added to validate the new functionality.

How can it be used:

• Dynamic Filter Behavior Adjustment: Users can decide whether to completely override the initial filters set during the retriever's initialization (replace) or merge them with runtime filters, with the latter taking precedence (merge).

• Complex Search Scenarios:

  • In cases where the context of a query might dictate altering pre-set filters without discarding them, the merge option allows for an additive approach.
  • For strict query contexts that require ignoring initial filters, the replace option offers a clean slate for filters at runtime.

How did you test it:

• Unit tests were enhanced or newly created to cover both replace and merge scenarios for the filter_policy parameter.
• Tests ensure that filter logic is correctly applied based on the policy setting, whether it merges runtime filters with initial filters or replaces them entirely.
• Additional test cases should be considered for complex filter merge scenarios to ensure priority and override mechanisms function as expected.

[davidsbatista]

it seems there's a test missing for this condition (filter_policy = 'merge'), no? and what happens if but for some reason filters = None

[vblagoje]

Yes, missing test, noted. If filters is None then else is executed and filters become either defined by user or {}

[vblagoje]

I'll add merge use case to all PRs

[vblagoje]

Please delay review until a new patch release of 2.2.x is released. We need these two PRs to be included in a patch release first.

[vblagoje]

Ready for review now @davidsbatista

• Since you last looked at this PR we introduced apply_filter_policy function that is used by all Retrievers in this PR and we thoroughly tested that function in that PR. We then just applied it here in run method
• Please note if FilterPolicy type is used consistently both in init and in run, and that it is documented well

[vblagoje]

Stefano recommended one more small improvement. Please hold your review until a new commit with it is added here

[vblagoje]

@davidsbatista please have a look at #827 @anakin87 has already gone through a through review of Astra and should help you validate this PR is well-aligned as well