User search dropdown should wait for controller response
Summary
Sometimes on user search, even if a user exists, dropdown shows "No result" and after sometime shows the found user.
This behavior can be observed on `meet.opentalk.eu`
Steps to reproduce the bug
On `meet.opentalk.eu` or simulate a slow internet connection and open network tab in dev tools
- Type in first three symbols for a user, that you know exists
- Observe that dropdown appears with "No result" option
- Observe in network tab that after some time a response has came from the controller
- Now the found user is rendered in the user search dropdown
Acceptance Criteria
- Render loading spinner while waiting for controller response