[calendar] multiple database entries for attendees when using drag & drop

Instead of updating the current database entry of the attendee, a new one is added when changing role/status by drag & drop

Reproduciability

Reproduciability
Yes
Steps (optionally)
Drag & Drop a guest

Message

Instead of updating the current database entry of the attendee, a new one is added when changing role/status by drag & drop

additional to that, the raidrgoup is set to 0 when changing status. And a new random value is added.

We need a cleaning function for this, keeping the newest entry only.

Comments 4