Plugin intercepts messages and checks if recipient is available. If not, plugin sends async POST request with JSON body to defined url.
Example JSON body:
        
            {
                "token":"21uh9d1h91d",
                "from":"user@mychatapp.com",
                "to":"user123@mychatapp.com",
                "body":"Message body, so what user's typed"
            }
        
    
plugin.callback_on_offline.debug - enable debug logs. If something doesn't work set property to trueplugin.callback_on_offline.url - url that will be calledplugin.callback_on_offline.token - token to be send with requestplugin.callback_on_offline.send_body - boolean value to determine if message's body will be send. True by default.