* [#523] added way to manage attendance for delegated calendars
* [DELEGATION] #523 & #524 changed eventURL calculation for delegated events to have the rigth one
* [#524] added drag and drop authorisation to delegated event
* [#524] added tests
* [#524] support for the permission access
* [#524] no edit when delegated event is not public
* [#490 & #489] Removed duplicated api call to get event data
* [#490] removed arbitrary timezone fallback to UTC/ETC & updated exdate formating
* [#490] updated test and fixed eventdiff utils to properly handle dates