refactor: Use UserService to update a user

[seakayone]

Pull Request Checklist

Task Description/Number

• Remove custom updateUser query and use UserService with UserRepo in order to update a user.
• Use a single query in UserRepo for save in both update and create cases.

PR Type

• build/chore: maintenance tasks (no production code change)
• docs: documentation changes (no production code change)
• feat: represents new features
• fix: represents bug fixes
• perf: performance improvements
• refactor: represents production code refactoring
• test: adding or refactoring tests (no production code change)

Basic requirements for bug fixes and features

• Tests for the changes have been added
• Docs have been added / updated

Does this PR introduce a breaking change?

• Yes

Does this PR change client-test-data?

• Yes

[codecov]

Codecov Report

Attention: 59 lines in your changes are missing coverage. Please review.

Comparison is base (eac5751) 11.74% compared to head (075833b) 12.01%.
Report is 73 commits behind head on main.

Files	Patch %	Lines
...knora/webapi/responders/admin/UsersResponder.scala	0.00%	36 Missing ⚠️
...ebapi/slice/admin/domain/service/UserService.scala	0.00%	13 Missing ⚠️
...api/slice/admin/api/service/UsersRestService.scala	0.00%	9 Missing ⚠️
...a/webapi/responders/admin/GroupsResponderADM.scala	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3053      +/-   ##
==========================================
+ Coverage   11.74%   12.01%   +0.27%     
==========================================
  Files         246      262      +16     
  Lines       22907    22699     -208     
==========================================
+ Hits         2690     2728      +38     
+ Misses      20217    19971     -246     

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[BalduinLandolt]

nice!