title: Calling cors(req,res,() => {}) without a req/res objects via a Firebase Functions trigger
body: <p>I'm trying to use cors(req,res,() => {... - it works well using the Firebase Functions HTTP function, but I want to call cors within a Firebase Functions trigger, which doesn't provide a req,res variables obviously.</p>
  
  <p>Cors seem to demand these parameters. How do I resolve it?</p>