If the input contains a valid IP address or range, show it in the autocomplete menu so that it can be selected.
After this, the widget should:
- Show no menu if the current input is not a valid IP address/range and doesn't complete to a username (as before)
- Show an autocomplete menu containing one or more usernames if the current input completes to any existing usernames (as before)
- Show an autocomplete menu containing the current input, if the input is a valid IP address or range
- When a menu option is selected, add a tag for it (as before)
- Add a tag for the current user input, even if it is not present in the menu (as before, until T238318 is solved)