Polar Webhook

Receive Polar webhooks — customer.state_changed only.

That event carries the customer's complete state (subscriptions, benefits, meters) rather than a diff, which makes the handler idempotent and immune to redelivery.

Acks immediately and does the DB write in a background task: Polar times out at 10 seconds and disables an endpoint after 10 consecutive non-2xx responses, with no dead-letter queue and no replay. So anything that is not "this request was forged" still returns 200 — a parse failure we can investigate in logs beats a disabled endpoint we discover a week later.

Deliberately unauthenticated: the Standard Webhooks signature is the authentication.