chore: Migrate to Java 21 and remove usage of Java 17 (DEV-3146)

[seakayone]

Pull Request Checklist

Task Description/Number

Issue Number: DEV-

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

[linear]

DEV-2815 dsp-api update Java 21

[codecov]

Codecov Report

Attention: 2 lines in your changes are missing coverage. Please review.

Comparison is base (eac5751) 11.74% compared to head (1a477d1) 88.54%.
Report is 3 commits behind head on main.

Files	Patch %	Lines
...ra/webapi/responders/admin/UsersResponderADM.scala	0.00%	1 Missing ⚠️
.../slice/admin/api/service/UsersADMRestService.scala	50.00%	1 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##             main    #2974       +/-   ##
===========================================
+ Coverage   11.74%   88.54%   +76.79%     
===========================================
  Files         246      249        +3     
  Lines       22907    22917       +10     
===========================================
+ Hits         2690    20291    +17601     
+ Misses      20217     2626    -17591     

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[linear]

DEV-3146 Update the dsp-api container to run with Java 21