Distribute invitations to group members

[cetcondor]

Is your feature request related to a problem? Please describe.
When you create a calendar date and want to invite colleagues to it, you have to add each individual manually. A time-consuming task.

Describe the solution you'd like
It would be really helpful that one can choose an entire group as participants. The group members should automatically receive individual invitations, so that each person can accept or decline.

Describe alternatives you've considered
A joint calendar would not help because the group members can not accept/decline individually.

Additional context
Consideration about compatibility with CalDAV: It's probably not necessary that Nextcloud 'remembers' that a group was invited. It is probably enough for most use-cases that the group is split up to individual persons once the invitations are out.

[ChristophWurst]

dup of #2955 or #167