Search for users after entering some chars (Video freigeben)

[dennis531]

Is your feature request related to a problem? Please describe.
Currently, the "Video freigeben" dialog shows a random set of users in the search dropdown. This leads to problems like mentioned in #1189.

Describe the solution you'd like
The search should be triggered after entering at least e.g. 3 characters as in the global user search. Below the limit the dropdown should show no users or not be expanded.

Screenshot