Fix pagination bug when only one field is selected and sorted at the same time

[adzialocha]

This PR fixes the issue we had when pagination suddenly broke for a query over one single sorted field.

We usually order by:

1. The field which was selected by the user to-be-ordered
2. document view id (except of when it was previously selected)
3. Cursor

Two things are important in this context:

• In SQL the ordering is only applied when the previous ordering stumbled upon duplicates
• The pagination logic needs to follow the same ordering to correctly paginate over it

When multiple fields have been selected by the user and we have duplicate values:

• We sort by documents (since we have 2 or more fields per document and we need to group them)
• .. And use the cursor finally as a tie-breaker for the duplicates

When one field has been selected and we have duplicate values there's an issue:

• We sort by documents, no duplicates are given here anymore because at this stage document view id's will be unique (when only one field is selected we always have a document per field)
• .. still we go by cursor to paginate even though this one became insignificant for the order

To fix this we simply just don't order by document id when sorting over one field!

Closes #583

📋 Checklist

• Add tests that cover your changes
• Add this PR to the Unreleased section in CHANGELOG.md
• Link this PR to any issues it closes
• New files contain a SPDX license header

[codecov]

Codecov Report

Attention: 1 lines in your changes are missing coverage. Please review.

Comparison is base (1a7cefc) 92.70% compared to head (4fd90dc) 92.79%.

Files	Patch %	Lines
aquadoggo/src/db/stores/query.rs	92.85%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #593      +/-   ##
==========================================
+ Coverage   92.70%   92.79%   +0.09%     
==========================================
  Files         106      106              
  Lines       18405    18623     +218     
==========================================
+ Hits        17062    17281     +219     
+ Misses       1343     1342       -1     

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