Resolve "Add admin dashboard with overview of slots"

What does this MR do?

Add a dashboard page for admins. Currently this will display the upcoming timeslot configurations and the ones which are passed. It will show the amount of time slots which are booked for each configuration as well as a button to edit them. Furhtermore it will also show the areas for which requests can be picked

Screenshots

before

after

Does this MR meet the acceptance criteria?

• I have added tests to validate the new functionality.
• I have updated the documentation accordingly.
• I have added translations for all new client-side text. closes #156 (closed) #214 (closed)