The SaaS can run your wasm code for you. In this case, you'd write the same code that you'd otherwise run in your infra to respond to the webhook, but it would be compiled to Wasm and run _in the SaaS app_ where the source event was triggered.

In your specific case, you'd still be making a call-out to your system to adjust the entitlements as you describe. However, many cases are actually taking action back on the SaaS side via API calls to the SaaS. So instead of a handful of back-and-forth calls over the Internet between you and SaaS, you just call their functions from the Wasm code running in their infra.