[TCC planning] Add option to create tccs/courses from multiple groups
In combination with #47 (closed), it should be possible to trigger the creation of a new course group with multiple parent groups by editing this raster.
I would suggest the following workflow:
- Add temporary column via plus button with multiple groups (just in frontend)
- When entering numbers, a matching course group is created (if the respective preference is turned on).
- Create course with new course group or with all groups selected, dependent on preference.
- Create TCC.