title: Create public REST API from firebase
body: <p>I am building a simple web app using Firebase as the backend. </p>
  
  <p>As part of that app I would like to expose a public API so that authenticated users can push or pull data from the app.</p>
  
  <p>However I do not wish to expose the generated URL that Firebase have provided me for development. </p>
  
  <p>Do I have to route requests to my API domain to Firebase through my app, or is there some way of giving a firebase API a public domain?</p>