MagicStarterStoreIds typedef
The store product ids a catalogue product is sold as, one per store, each
null when that store does not carry it.
play is Google Play's subscriptionId:basePlanId. These are what a store
receipt names, so they are how a held store subscription is placed on a tier;
a purchase still names the catalogue key, never one of these.
Implementation
typedef MagicStarterStoreIds = ({String? appStore, String? play});