Add an overview of all lessons for teachers and coordinators

In the specifications, it was listed that grade leaders can open an overview of the lessons of the classes that are assigned to them in order to mark missing entries and ask the teachers concerned by mail to fill in the gaps. In addition, it would be necessary for teachers to receive a compact list of their own lessons in order to get a quick overview of missing entries.

The menu item "My overview" would be useful for both requirements, if the call shows a different list of hours depending on the role (student, teacher, level leader). Teachers should be able to select period and class via a filter.