fix: Properly validate repository name in frontend and backend

[dominik003]

Resolved #1170

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (7af54dd) 72.50% compared to head (d5b730c) 72.50%.
Report is 4 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1178   +/-   ##
=======================================
  Coverage   72.50%   72.50%           
=======================================
  Files         162      162           
  Lines        5289     5289           
  Branches      592      592           
=======================================
  Hits         3835     3835           
  Misses       1322     1322           
  Partials      132      132           

Files	Coverage Δ
...b/settings/modelsources/t4c/repositories/models.py	100.00% <100.00%> (ø)

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[sonarcloud]

Kudos, SonarCloud Quality Gate passed!   

0 Bugs
0 Vulnerabilities
0 Security Hotspots
0 Code Smells

No Coverage information
0.0% Duplication