[TCC planning] Add option to create course groups

We should allow users to automatically create course groups instead of using the class groups. If this option is activated (either as checkbox on the page or as preference, I prefer the latter), a new group should be created with the original group as parent group.

added part::frontend source::customer::kath type::feature labels

assigned to @yuha

mentioned in issue #48

changed milestone to /AlekSIS%"[NLnet #1 (closed)] Fix existing bugs with new timetable"

created branch 47-tcc-planning-add-option-to-create-course-groups to address this issue

mentioned in merge request !45 (merged)

@hansegucker what group should be set as parent group when multiple groups are specified during course creation? (e.g. "5abcd-La")?

mentioned in commit e9aa7184

closed with merge request !45 (merged)