GitLab

Service layer (payment_fulfillment_order_not_found_test.go):
- TestHandlePaymentNotification_UnknownOrder_ReturnsSentinel: in-memory
  sqlite ent client, query for a non-existent out_trade_no → errors.Is
  must recognise ErrOrderNotFound (handler relies on this to ack 200).
- TestHandlePaymentNotification_NonSuccessStatus_Skips: non-success
  notification short-circuits before DB lookup → nil error.
- TestErrOrderNotFound_DistinctFromOtherErrors: generic errors must not
  match the sentinel (prevents silently swallowing DB failures).

Handler layer (payment_webhook_handler_test.go):
- TestUnknownOrderWebhookAcksWithSuccess: locks the two ingredients the
  handleNotify ack path depends on — fmt.Errorf %w wrapping preserves
  errors.Is recognition, and writeSuccessResponse(stripe) returns an
  empty 200 body that Stripe treats as acknowledged.

Add a full payment and subscription system supporting EasyPay (Alipay/WeChat),
Stripe, and direct Alipay/WeChat Pay providers with multi-instance load balancing.