Keeping the overview of all timetables up to date

In the overview of all timetables, teachers are displayed who were active in past periods and not in the current period. The filter would have to be restricted to the current school term.

added part::backend source::customer type::bug labels

assigned to @hansegucker

created merge request !245 (merged) to address this issue

mentioned in merge request !245 (merged)

closed with commit cf095d0b

mentioned in commit cf095d0b