add test case from issue #500

src/icalendar/tests/events/event_with_rsvp.ics

@@ -0,0 +1,3 @@
+BEGIN:VEVENT
+ATTENDEE;RSVP=TRUE:mailto:someone@example.com
+END:VEVENT

src/icalendar/tests/test_issue_500_vboolean_for_parameter.py

@@ -0,0 +1,9 @@
+from icalendar import Event, vBoolean, vCalAddress
+
+def test_vBoolean_can_be_used_as_parameter_issue_500(events):
+    '''https://github.com/collective/icalendar/issues/500'''
+    attendee = vCalAddress(f'mailto:someone@example.com')
+    attendee.params['rsvp'] = vBoolean(True)
+    event = Event()
+    event.add('attendee', attendee)
+    assert event.to_ical() == events.event_with_rsvp.raw_ics