A toggle to make herself available / unavailable for receiving Calls
Missing permissions
The availability toggle should not be enabled if the required browser permissions for notification display and a webpush subcription is gratnted. Instead, the UI of the toggle should remain on the unavailable state and a text message saying that the permission is required displayed.
Error messages
The UI should display error messages if the API call for user update (after browser gets a webpush subscription) or availability update fails.
fczuardi
commented
7 years ago 
The main screen of the app, should display:
Missing permissions
The availability toggle should not be enabled if the required browser permissions for notification display and a webpush subcription is gratnted. Instead, the UI of the toggle should remain on the unavailable state and a text message saying that the permission is required displayed.
Error messages
The UI should display error messages if the API call for user update (after browser gets a webpush subscription) or availability update fails.