[DOP-19835] Fix GET /v1/groups skipping some groups

[dolfinus]

Change Summary

When Group had a lot of bound UserGroup rows, the page limit in GET /v1/groups was applied to these rows instead of distinct Groups. Fixed.

Also fix missing "Authorize" button in Swagger.

Related issue number

Checklist

• Commit message and PR title is comprehensive
• Keep the change as small as possible
• Unit and integration tests for the changes exist
• Tests pass on CI and coverage does not decrease
• Documentation reflects the changes where applicable
• docs/changelog/next_release/<pull request or issue id>.<change type>.rst file added describing change
  (see CONTRIBUTING.rst for details.)
• My PR is ready to review.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 92.92%. Comparing base (11e7910) to head (cbd294c).
Report is 97 commits behind head on develop.

Additional details and impacted files

@@             Coverage Diff             @@
##           develop      #84      +/-   ##
===========================================
+ Coverage    92.82%   92.92%   +0.09%     
===========================================
  Files           84       84              
  Lines         2452     2444       -8     
  Branches       309      307       -2     
===========================================
- Hits          2276     2271       -5     
+ Misses         123      121       -2     
+ Partials        53       52       -1     

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