i have a nodejs docker image app deployed on gke (gcp). This app is just a message subscriber which waits to be notified. I've created a topic (pubsub). iam trying to add a subscription so my app could be notified. but i didn't manage to do it. I tried to add the ip (domain) in google credentials (APIs & Services/credentials) but the process is really shady. Why verify an app deployed in gcp ?? Is there any way around ? thanks