core: Block usage of Django's createsuperuser

[dominic-r]

django’s default create_superuser tries to set is_staff/is_superuser, but our User exposes these as read-only properties which are derived from group membershp

that would cause the attribute error seen in the user report.

Closes: #16212

Details

REPLACE ME

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Checklist

• Local tests pass (ak test authentik/)
• The code has been formatted (make lint-fix)

If an API change has been made

• The API schema has been updated (make gen-build)

If changes to the frontend have been made

• The code has been formatted (make web)

If applicable

• The documentation has been updated
• The documentation has been formatted (make docs)

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 92.77%. Comparing base (1c36b36) to head (f55a1e5).
⚠️ Report is 3 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #16215      +/-   ##
==========================================
- Coverage   92.77%   92.77%   -0.01%     
==========================================
  Files         837      837              
  Lines       45244    45244              
==========================================
- Hits        41975    41973       -2     
- Misses       3269     3271       +2     

Flag	Coverage Δ
e2e	46.69% <ø> (+0.07%)	⬆️
integration	23.49% <ø> (-0.06%)	⬇️
unit	90.92% <ø> (+<0.01%)	⬆️

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[dominic-r]

cc @rissson