结账：风险、测试与操作
定义了一个服务器权威的结账工作流程，包含定价快照、幂等的提供者会话、经过验证的异步履行、库存或权益保障以及对账证据。
Defines a subscription integration that separates provider objects, internal service periods, money movements, and entitlement state so retries, prorations, cancellations, and reconciliation remain auditable.