Event results might not be valid ICS

[niccokunzmann]

Describe the bug

When I have an event with the attribute DURATION (https://www.rfc-editor.org/rfc/rfc5545#section-3.8.2.5), then the value DTEND is still set. This makes it an invalid event for to_ical(): DTEND and DURATION MUST not occur at the same time. This might not be so much of an issue but it could be. This should be checked.

To Reproduce

Get the events from the example with duration
See that DTEND and DURATION are both possible.

ICS file

https://github.com/niccokunzmann/python-recurring-ical-events/blob/main/test/calendars/duration-edited.ics

Expected behavior

I would opt for removing DURATION like RDATE and such, as written in https://github.com/niccokunzmann/python-recurring-ical-events?tab=readme-ov-file#events-as-list

Console output

Version:

Additional context

Suggested implementation

• add an ICS file, example:
  

  python-recurring-ical-events/test/calendars/issue-15-duplicated-events.ics

  Line 1 in f4a90b2

  BEGIN:VCALENDAR

• add a test, example:
  

  python-recurring-ical-events/test/test_issue_15.py

  Line 21 in f4a90b2

  def test_sequence_is_not_present(calendars):

• fix the bug and ensure the test code passes

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