feat: Level access control logic

[faucomte97]

This change is 

[KamilPawel]

Reviewed 14 of 14 files at r1, all commit messages.
Reviewable status: complete! all files reviewed, all discussions resolved (waiting on @faucomte97)

[codecov]

Codecov Report

Merging #1379 (8f41cd1) into master (3f22487) will decrease coverage by 0.07%.
The diff coverage is 95.34%.

@@            Coverage Diff             @@
##           master    #1379      +/-   ##
==========================================
- Coverage   91.80%   91.72%   -0.08%     
==========================================
  Files          98       99       +1     
  Lines        5457     5477      +20     
==========================================
+ Hits         5010     5024      +14     
- Misses        447      453       +6     

Impacted Files	Coverage Δ
example_project/rapid_router_test_settings.py	100.00% <ø> (ø)
example_project/settings.py	0.00% <ø> (ø)
game/urls.py	100.00% <ø> (ø)
game/views/level.py	71.14% <90.90%> (+1.35%)	⬆️
game/admin.py	100.00% <100.00%> (ø)
game/migrations/0076_level_locked_for_class.py	100.00% <100.00%> (ø)
game/models.py	95.00% <100.00%> (+0.04%)	⬆️
game/permissions.py	72.72% <100.00%> (-5.06%)	⬇️
game/views/level_selection.py	92.24% <100.00%> (+0.27%)	⬆️

[KamilPawel]

Reviewable status: complete! all files reviewed, all discussions resolved (waiting on @faucomte97)