databasus/backend/internal/features/billing/paddle/README.md

Paddle hints:

• max_quantity on price: Paddle limits quantity on a price to 100 by default. You need to explicitly set the range (quantity: {minimum: 20, maximum: 10000}) when creating a price via API or dashboard. Otherwise requests with quantity > 100 will return an error.
• Full items list on update: Unlike Stripe, Paddle requires sending all subscription items in PATCH /subscriptions/{id}, not just the changed ones. proration_billing_mode is also required. Without this you can accidentally remove a line item or get a 400.
• Webhook events mapping: Paddle uses transaction.completed instead of payment.succeeded, transaction.payment_failed instead of payment.failed, adjustment.created instead of dispute.created.