code: function onLinkWithEmailLink() {
    var email = $('#link-with-email-link-email').val();
    var link = $('#link-with-email-link-link').val() || undefined;
    var credential = firebase.auth.EmailAuthProvider
        .credentialWithLink(email, link);
    activeUser().linkWithCredential(credential)
        .then(onAuthUserCredentialSuccess, onAuthError);
  }
docs: Links a user with an email link.