Support collections in multi_search

[ellnix]

Pull Request

Related issue

Fixes part of #397

• This makes multi_search, like the regular search, support relations and other collections that respond to where.
• In favor of this new :collection option, :class_name is softly deprecated for a consistent user experience (since :collection does everything that :class_name did and more)

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 89.61%. Comparing base (5450df2) to head (d969d9b).

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #405      +/-   ##
==========================================
+ Coverage   89.54%   89.61%   +0.06%     
==========================================
  Files          13       13              
  Lines         775      780       +5     
==========================================
+ Hits          694      699       +5     
  Misses         81       81              

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[ellnix]

@pozelli Please review and see if this makes multi_search behave how you expect it to 😄

@wesharper If you are interested in doing code review please take a look at this PR. (if you are not interested that's OK, it's not an assignment 😆 think of it more like a +cc)

[pozelli]

@pozelli Please review and see if this makes multi_search behave how you expect it to 😄

Sure.

This PR addresses these items from #397:

Currently, multi_search (e.g., in FederatedSearchResult) does not seem to support queries on collections. It only works with models or simple indexes.

In a federated search, since it is not possible to use collections but only models or simple indexes, I must first perform an additional step: Queries to retrieve the IDs of each record.

This extra query could already be avoided if federated search supported collections, just as simple search does.

On the other hand:

However, we would still face the pagination issue.

I have tested the PR, and it works as I expected it to.