refactor: Migrate GET /admin/users/iri/<userIri> to tapir

[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

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (eac5751) 11.74% compared to head (50f9172) 88.53%.
Report is 33 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff             @@
##             main    #3010       +/-   ##
===========================================
+ Coverage   11.74%   88.53%   +76.79%     
===========================================
  Files         246      262       +16     
  Lines       22907    23090      +183     
===========================================
+ Hits         2690    20443    +17753     
+ Misses      20217     2647    -17570     

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