events: Fix last day of web calendar for full-day event

In the events model, an event with an end_date but without an end_time is
meant to include the last day. Fullcalendar.io, which is used for the
web calendar, however, always regards the end datetime as exclusive.

Add a day in the case that we have no end_time, so that the web calender
includes the last day in the display.

mpicms/events/models.py

@@ -1,5 +1,5 @@
 import json
-from datetime import datetime, date
+from datetime import datetime, date, timedelta
 from ics import Calendar, Event as ICSEvent
 
 from django.db import models
@@ -71,10 +71,15 @@ def end(self):
         return self.end_date
 
     def get_dict(self, request=None):
+
+        datetime_end = self.end
+        if self.end_date and not self.end_time:
+            datetime_end += timedelta(days = 1)
+
         return {
             'title': self.title,
             'start': self.start.isoformat(),
-            'end': self.end.isoformat() if self.end else None,
+            'end': datetime_end.isoformat() if self.end else None,
             'url': self.get_url(request=request),
         }