Add or complete docstrings
Remove code smells
Disable irrelevant warnings
Remove empty admin.py (to disable doc generation for an empty module)
Add additional test cases and improve basic test interface (support both 403 and 302 in case the user lacks rights to see a view through optional configuration)
Improve usage of types for API endpoints (e.g., restrict writing endpoints to writing only)

I think, that makes sense since it is supposed to be used by the graphical scheduling view

Implements #147