The Play subscription check reads purchases.subscriptionsv2 by token
through the existing service-account client, with the same HTTP classes as
product reads, and maps Play's state, base plan, period, order id and
offer phase; the period start is its end minus the plan's length, and a
pending subscription stays pending. A subscription is acknowledged with
purchases.subscriptions.acknowledge before it is credited, skipped when
Play reports it acknowledged, so it never reaches the one-time endpoint.
Each store's subscriptions answer provider_not_configured when that store
is not configured. A charge on a plan the catalog does not sell is pending
rather than a malformed period.
Run: 001-badge-subscriptions, slice 7