A mountable livery handler for the Stripe webhook endpoint.

Add it to a router with routes/0,1:

livery_router:compile(livery_stripe_webhook_handler:routes()).

handle/1 reads the raw body and Stripe-Signature header, verifies the event with livery_stripe_webhook, and dispatches it to the configured callback (the webhook_callback config key). It always answers JSON: 200 when accepted, 400 on a bad payload or signature.

The callback may be a fun/1 (Event), a fun/2 (Type, Event), a module implementing handle_event/2, or a {Module, Function} pair. Persistence (updating a user's subscription, etc.) belongs in the callback; this module stays storage-agnostic.