title: Cloud Functions for Firebase - Billing account not configured
body: <p>I just implemented the new Cloud Functions for Firebase, but there something in the log that bothers me:</p>
  
  <blockquote>
    <p>Billing account not configured. External network is not accessible and
    quotas are severily limited. Configure billing account to remove these
    restrictions</p>
  </blockquote>
  
  <p>I actually managed to access the function from the external network, so I'm wondering do I really have to give my billing account? There's nothing about this in the firebase documentation.</p>
  
  <p>I'm using the Spark subscription plan for personal test purposes and I don't want to add billing info if I'm not going to pay for anything yet.</p>