title: Firebase not uploading to firestore using .doc
body: <p>I am trying to use firebase and stripe to set up payments on my website based on the source code found here: <a href="https://github.com/firebase/functions-samples/tree/master/stripe" rel="nofollow noreferrer">https://github.com/firebase/functions-samples/tree/master/stripe</a>
  I've tried resetting my rules for firestore and realtime database, but I keep getting stuck on .snapshot. I've looked in the debugger, and currentUser.uid is not null, but it is not creating a new entry in the database. Any help on this would be greatly appreciated! First time using firebase so I am a little lost. At the moment, my rules files are the same as those linked in the github repo.</p>
  <pre><code>firebase.auth().onAuthStateChanged((firebaseUser) =&gt; {
    if (firebaseUser) {
      currentUser = firebaseUser;
      firebase
        .firestore()
        .collection('stripe_customers')
        .doc(currentUser.uid)
        .onSnapshot((snapshot) =&gt; {
          if (snapshot.data()) {
            customerData = snapshot.data();
            startDataListeners();
            document.getElementById('loader').style.display = 'none';
            document.getElementById('content').style.display = 'block';
          } else {
            console.warn(
              `No Stripe customer found in Firestore for user: ${currentUser.uid}`
            );
          }
        });
    } else {
      document.getElementById('content').style.display = 'none';
      firebaseUI.start('#firebaseui-auth-container', firebaseUiConfig);
    }
  });
  </code></pre>