refactor: Migrate GET /admin/users/<iri|email|name> 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 (e2e8fb8) 88.51%.
Report is 49 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff             @@
##             main    #3020       +/-   ##
===========================================
+ Coverage   11.74%   88.51%   +76.76%     
===========================================
  Files         246      258       +12     
  Lines       22907    22826       -81     
===========================================
+ Hits         2690    20204    +17514     
+ Misses      20217     2622    -17595     

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[mpro7]

Just one question/suggestion below: