Support invite-rsvp-checkstatus calendar workflow with exchange

[dphi]

It would be great if the nextcloud server caldav component would be more compatible with Exchange(+Outlook) users.

NC invites Outlook

1. Invitation is send to Exchange
2. No Accept/ Decline/ Tentative buttons visible that would update
   Expected behavior: Accept/ Decline/ Tentative buttons are visible and these responses are being send back to the inviting user

Outlook invites NC

1. Invitation is send to NC
2. Aceept/ Decline/ Tentative buttons are visible
3. The status is visible in the NC client
4. The RSVP status update is send via SMTP to exchange.
5. The iCal-Reply.ics attached to the previous mail is not recognised by Exchange as such and thus not used to update the RSVP status of the calendar entry
   Expected behavior: Exchange detects the ical-reply.ics as such and updates the participants RSVP status.

The RSVP buttons developed for NC14 do solve this.

(I tested using macos 10.13 as a client for NC.)

[nextcloud-bot]

GitMate.io thinks possibly related issues are #5050 (CalDAV: Support calendar sharing via MacOS Calendar.app), #3161 (Support HHVM), #2494 (Sqlite support), #3805 (predis support), and #3761 (PostgreSQL support).

[szaimen]

I am going to close this since there doesn't seem to be a lot of interest (no upvotes) and no respond since around 2 years. Please reopen if you still want to implement this.