Send invitations via Mail

[ghost]

I am actually not sure if this handled by the "sync-adapter" like offline-calendar or the "calendar app" like your standalone-aosp-calendar, so please point me to the right direction:

Adding guests/attendees to an event should send an email with an attached ics file to those guests. This should be done via a mailto URI, like the "quick response" feature does (which allows you to send a prepopulated mail -- e.g. "be there in x minutes" -- to all attendees.

Since exporting an ics is somewhat cumbersome and not all mail clients parse mailto uris completly, an initial implementaion could just send the dates and subject of an event in the mail body.