chore: Enable Rubocop for migrations

[arkirchner]

Rubocop gives valuable information about issues in migration. New migrations should be checked by the linter.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 70.08%. Comparing base (ea29353) to head (73bb7fa).
⚠️ Report is 10 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #3045   +/-   ##
=======================================
  Coverage   70.08%   70.08%           
=======================================
  Files         215      215           
  Lines        6850     6850           
=======================================
  Hits         4801     4801           
  Misses       2049     2049           

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[kkoehn]

This is great, I didn't know this existed!

[MrSerth]

@arkirchner Could you please apply the same changes in CodeHarbor, since the Rubocop configuration is closely set in both projects?

[MrSerth]

Thanks for adding similar changes in CodeHarbor with openHPI/codeharbor#2092.