Base class for the server implementation of the service ConsumerProcurementService.
ConsumerProcurementService allows customers to make purchases of products
served by the Cloud Commerce platform.
When purchases are made, the
[ConsumerProcurementService][google.cloud.commerce.consumer.procurement.v1alpha1.ConsumerProcurementService]
programs the appropriate backends, including both Google's own
infrastructure, as well as third-party systems, and to enable billing setup
for charging for the procured item.