Issue submitted to https://www.apple.com/feedback/calendar.html:
This technical issue is described here : https://github.com/fruux/sabre-vobject/issues/227
Context: we use a custom calendar account in a custom Fruux Sabre-dav calendar server, RFC compliant.
Summary: if Calendar send a vCalendar request to our calendar server with an URL field having VALUE=URI, as in :
URL;VALUE=URI:http://foo.com/event/95