Enable the authuser to be a string

[alejandroivan]

The authuser URL parameter can also be a string.

Meet/Gmail/etc. accept URLs in the form:

• https://meet.google.com/meeting-id/?authuser=1
• https://meet.google.com/meeting-id/[email protected]

So it would be nice for the options dialog to not restrict the authUser as an int, but let it be an email string.

This is also useful for the authuser to be always correct, no matter in which order you log in into your accounts.

[lesiki]

Great idea, I didn't realize it works with email address as a string.