title: ICS File not showing RSVP button due
body: <p>I've been having an issue with the RSVP options showing up when I send out a calendar invite. It seems like it may be an issue with my RRULE by some reason.
  When I use the following code for the ICS file it does not show the RSVP button </p>
  
  <pre><code>BEGIN:VCALENDAR
  METHOD:REQUEST
  PRODID:Data::-//foo
  VERSION:2.0
  BEGIN:VTIMEZONE
  TZID:Eastern Standard Time
  X-LIC-LOCATION:America/New_York
  BEGIN:STANDARD
  DTSTART:16011104T020000
  RRULE:FREQ=YEARLY;BYMONTH=11;BYDAY=1SU
  TZOFFSETFROM:-0400
  TZOFFSETTO:-0500
  END:STANDARD
  BEGIN:DAYLIGHT
  DTSTART:16010311T020000
  RRULE:FREQ=YEARLY;BYMONTH=3;BYDAY=2SU
  TZOFFSETFROM:-0500
  TZOFFSETTO:-0400
  END:DAYLIGHT
  END:VTIMEZONE
  BEGIN:VEVENT
  ATTENDEE;CN="Test";RSVP=TRUE:mailto:test@test.com
  SEQUENCE:17
  DTSTAMP:20180517T122445
  DTSTART;TZID="Eastern Standard Time":20180518T000000
  DTEND;TZID="Eastern Standard Time":20180518T010000
  SUMMARY;LANGUAGE=en-US:Test - May 18\, 2018
  ORGANIZER;CN="Test":mailto:test@test.org
  LOCATION:Mars
  STATUS:CONFIRMED
  RRULE:FREQ=WEEKLY;UNTIL=20180720T000000;INTERVAL=1;BYDAY=FR;WKST=SU
  UID:68588Atest@test.com
  END:VEVENT
  END:VCALENDAR
  </code></pre>
  
  <p>Any help would be appreciated! Thanks!</p>