title: Firebase web client and OIDC Provider issues
body: <p>I have configured an OIDC provider (linked to a Keycloak OIDC provider) in Google Identity Platform console. This is the code in my single page app: </p>
  
  <pre><code>provider = new firebase.auth.OAuthProvider('oidc.keycloak');
  firebaseAuth.auth.signInWithPopup(provider)
        .then(value =&gt; {
          log.info(`It worked!`, value);
        })
        .catch(err =&gt; {
          log.info('Something went wrong:', err);
        });
  </code></pre>
  
  <p>The popup window appears and I can login to Keycloak, but after the popup disappears the following error is thrown in the browser:</p>
  
  <pre><code>{code: "auth/admin-restricted-operation", message: "This operation is restricted to administrators only."}
  </code></pre>
  
  <p>I am using the latest versions of Firebase Client SDK and AngularFire2 and I have successfully configured Email/Password authentication.
  In Google Identity Platform I have:</p>
  
  <p>Issuer (URL): </p>
  
  <pre><code>https://auth.example.com/auth/realms/myrealm
  </code></pre>
  
  <p>and 
  Callback URL: </p>
  
  <pre><code>https://myapp-12345.firebaseapp.com/__/auth/handler
  </code></pre>
  
  <p>Is there an additional configuration in the client side that I need to do? Could the issue be with the OIDC provider (Keycloak) and its configuration?</p>