Nope it is not the google cloud service. Google cloud service is fcm. (Firebase Cloud Messaging - Google)
I installed the plugin: "Google Devices - Chromecast and Home". By this, there is a new notification option in the notification settings of switches, called: "Google_Devices". So my guess was to put it in the .lua config and it would work, it does not.
Although it would be very simple if it would work this way.
But ill go and take a look at what you are doing with node-red-contrib-cast. All new to me, but its fun to explore.
Thanks.
Google Devices - Chromecast and Home:
https://github.com/dnpwwo/Domoticz-Google-Plugin