title: How to confirm credentials while the user is logged in? (on Firebase)
body: <p>I am using <code>Firebase</code> in an <code>iOS</code> app to provide server support to the users.
  When someone wants to change his credentials (email/password) or his display name, I request to confirm the current credentials. Is there a way (an API) to check that the provided credentials are the ones matching the currently logged in user, other than perform a log out and trying to log in again, hoping the provided credentials are correct?</p>