Creem Payment Provider

Add creemPaymentProvider() to PaymentService.providers. CREEM_API_KEY, CREEM_PRODUCT_ID, and CREEM_WEBHOOK_SECRET are all required. CREEM_PRODUCT_ID must reference a one-time product with tax included in its price, and CREEM_CURRENCY must match that product's currency. Payment passes the server-side order amount as Creem custom_price, which must be between 100 and 99,999,999 minor currency units.

await city.payment.method("creem").invoke({ topup_amount_minor: 500, idempotency_key: "order_123" });

Use on_paid(record) to call credits.topup() idempotently with payment:${record.payment_id}.