Shared management of a form

[uli-heller]

Nextcloud (please complete the following information):

• Nextcloud-Version: 20.0.3
• Forms-Version: 2.0.4

Is your feature request related to a problem? Please describe.
I use "forms" for example to make sure people do a couple of actions before leaving for vacation.
The list of actions needs to be modified from time to time. I wish that I could transfer the ownership
of my "form" to another user in order not to be the only one who can modify the form.

Describe the solution you'd like
Invite other users to "manage" a form I created

[skjnldsv]

Duplicate of #322