I can't find a document or blog post to corroborate my findings, but it seems like Hangouts API no longer sends verification tokens along with messages. This is probably because receiving messages via Pub/Sub platform, using a service account, would be considered sufficient authentication.
Granted, this is a brand new deployment, so I am wide open to be proven wrong. I never had a Hangouts bot before, so I don't know what happens to old deployments. All I know is that if you create a new Pub/Sub, the Hangouts API does not expose the verification tokens. I have confirmed that with a friend's account.
I can't find a document or blog post to corroborate my findings, but it seems like Hangouts API no longer sends verification tokens along with messages. This is probably because receiving messages via Pub/Sub platform, using a service account, would be considered sufficient authentication.
Granted, this is a brand new deployment, so I am wide open to be proven wrong. I never had a Hangouts bot before, so I don't know what happens to old deployments. All I know is that if you create a new Pub/Sub, the Hangouts API does not expose the verification tokens. I have confirmed that with a friend's account.