Scenarios with only messages with "REMOVE" or "FIRSTVEJO" as messagedurationtype will no longer require/show endtime in planning-form:
In case of scenarios with mixed messagedurationtypes the form will show that the endtime will only apply to messages with messagedurationtype "ENDTIME":
Starttime and endtime will be validated to prevent django-crashes and log-errors.
Within the 'actieve berichten' of the 'berichten'-page, messages without endtimes are now shown as well until deleted.