Clean-up models and remove unnecessary fields

Some fields in the Timeslot model are no longer required or can be exposed through the serializers and will be removed: note_id and show.

changed milestone to %1.0-alpha3 — Playful Platypus

assigned to @eigenwijsje

added P3 label

added 1 deleted label

added To Do label

changed the description

added Doing label and removed To Do label

mentioned in commit d704292a

removed Doing label

closed

The changes are implemented in the develop branch:

The fields have been removed from the model.

The /api/v1/timeslots/ endpoint still contains the read-only fields noteId and showId.