title: How can I login with multiple social services with Firebase?
body: <p>I want users to be able to authenticate to my Firebase application using multiple different auth providers, such as Facebook, Twitter, or Github. Once authenticated, I want users to have access to the same account no matter which auth method they used.</p>
  
  <p>In other words, I want to merge multiple auth methods into a single account within my app. How can I do this in a Firebase app?</p>