In what use cases can user-provided wasm realistically replace webhooks? It seems to me that in plenty of cases, you'd end up needing something like webhooks anyway. For instance, I use Stripe, and I implement their webhook to handle completed checkouts. My webhook implementation needs to update my database, send email using my email service provider credentials, etc. I doubt that running my own wasm code on Stripe's infrastructure would make things simpler. But I'd like to learn more on use cases where user-provided wasm really would be better.