Deprecated: many authentication providers no longer pass along the users name so this function will often return blank. Use the
USEREMAIL() function to identify a user.
USERNAME() returns the name of the current user.
The user's name is obtained from the service through which the user logs into the app. If the user is not logged in, the name is not available. Even for logged-in users, not all authentication providers make the user's name available.
Name value: the name of the current logged-in user if provided by the authentication provider, or blank otherwise.