Stripe webhook signature verifier.
Delegates to SkillKit.Webhook.Verifier.Hmac with Stripe's well-known
scheme baked in: HMAC-SHA256 over "<timestamp>.<body>", with both the
timestamp and the signature pulled from the Stripe-Signature header.
Registration config (passed through)
secret_key(required) — the key name resolved viaCredentialProvider.max_skew(optional) — timestamp tolerance in seconds. Default 300.