Package-level declarations

Adapts the gateway's chargeback callback, ChargebackNotified, mounted under the payment: the refund of the payment it names. The command's headers keep the dispute (DISPUTE_ID), and so does the payment's event stream.

The eShop's payment service on the Wow host: the host finds the payment model and the sagas through eshop-payment-domain's binding index and serves its routes on the public port and the cluster on the internal one. It runs on the memory backend by default and on PostgreSQL with the postgres profile (spring.datasource.*).

The payment service's command transformers, one per command type they take.