Calendar app ignores exception to recurrence if value is `DATE` instead of `DATE-TIME`.

The iCalendar format has an EXDATE property to store the exception to event recurrence. According to RFC5545, 3.8.5.1, this property can have either a DATE or a DATE-TIME as its value. Nextcloud Calendar respects the exception if the value is a DATE-TIME, but ignores it if the value is DATE.

Steps to reproduce

1. Create a calendar entry with recurrence.
2. Delete one recurrence in Nextcloud Calendar (thereby creating an EXDATE entry with a DATE-TIME value).
3. Add another EXDATE exception via CalDAV, with a DATE value.
4. Verify that the iCalendar has two EXDATE properties similar to:

   EXDATE;TZID=timezone:2021mmddThhmmss
   EXDATE;VALUE=DATE:2021mmdd
   

Expected behaviour

For both exceptions, no event should be displayed in Nextcloud Calendar.

Actual behaviour

No event is displayed in Nextcloud Calendar for the DATE-TIME exception. However, the DATE exception is ignored.

Calendar app

Calendar app version: 2.3.4

Start by reproducing the issue with a recurring event containing both DATE-TIME and DATE EXDATE values, using the RFC5545 section cited in the report as the format reference. Trace how the Calendar app parses and displays recurrence exceptions. Done means both exceptions prevent their corresponding event occurrences from being displayed.