Create a RegisterObjectModel superclass for LessonPeriod, Event and ExtraLesson

They are really similar models used in the same places. Often you want a ForeignKey to exactly one object from one of these model classes

added part::backend prio::1 type::refactoring labels

added workflow::discussing label

assigned to @hansegucker

unassigned @hansegucker

assigned to @hansegucker

unassigned @hansegucker

Outdated due to new data model.

closed