L3 - Default Context:
To simplify the mapping of events we should only allow one mapping for them. Timer events will implicitly get der duration assigned from adjacent events in the backend.
AT:
- events from the event table can only be mapped as `Start` to event flow nodes/activities, the Mapped as dropdown is disabled for events except timerEvents, for timer events user can either select Start or end but still just apply one mapping
- the new default option in the Mappes As Dropdown is `Start`
