I'd like to able to detect a successful arb payment so that I can send our user's emails when their payment has gone through. I figured I would be able to use webhooks. However, the webhook documentation doesn't make it clear how to detect a successful arb payment.

I couldn't figure out what to expect from the documentation, so I created a webhook endpoint that records what gets sent to it, then I created a subscription and waited to receive a webhook notification. The problem is that when I did get a notification, the authMount value was 0.0. In the sandbox dashboard, I can see the subscription, and it says the amount is $199, and that 1 payment has gone through.

So, my question is this: How do I detect a successful subscription payment? Is it normal for a subscription notification to have an authAmount of 0.0, or is this a bug in the sandbox env? Please advise me how to detect a successful subscription payment with webhooks.