title: Firebase-how to use a username along with google sign in?
body: <p>I recently added google sign in with firebase to my website which already uses sign in with email and password. My website already has a lot of stuff involving their username (I have a separate database with email id and username, so I log them in using their email even if they give their username). So now, when a person signs in with google for the first time, it should save their google username and email in that database. How do I do this?</p>