We developed this backend using Firebase, Google Cloud, and JS and tested it with Postman. One endpoint is adding a message, in which you would send data in json form like this
{ "data": { "text": "Hello this is a test message", "userId": "dsds" } }
to our endpoint hosted on Google Cloud.
if all goes right, we'll receive the status "success" along with the messageId as a form of communication and authentication.