core: record the device store's view of a subscription

The service reads the store only once a subscription's paid coverage has
ended, so it never sees a cancellation while the period runs. The apps read
the device's store (StoreKit's renewal state, Play's isAutoRenewing) and
report it with /_badge subscription <state> <payment>, which records it on
the credited subscription purchase the payment resolves to and announces the
change to its owner.

A renewing report does not replace billingRetry or ended: Play lists a
subscription in its grace period with auto-renew on, and the service's next
answer clears billing retry once the charge lands.

Run: 003-badge-subscriptions-ui, slice 3

bots/src/API/Docs/Commands.hs

@@ -430,6 +430,7 @@ undocumentedCommands =
     "APISendCallOffer",
     "APISendServiceRequest",
     "APISetAppFilePaths",
+    "APISetBadgeSubscriptionStatus",
     "APISetChatItemTTL",
     "APISetChatSettings",
     "APISetChatTags",