[feature] provide FeatureStore about platform

[MikeRyanDev]

Your solution is how we would recommend going about this. We thought long and hard about whether or not we should scope instances of Store to feature state and ultimately came to the conclusion that - while powerful - it can be very confusing to track what instances of Store are received by which components. It also complicates deriving state from multiple features, a pattern that is common in our own applications.

[amitport]

The current way I'm doing this

const ROOT_STORE = new InjectionToken<Store<MyAppState>>('rootStore');

in root module:
{provide: ROOT_STORE, useExisting: Store}

in child module:
{ provide: Store, useFactory: (store: Store<MyAppState>) => store.select(createFeatureSelector<MyFeatureState>('myFeature')), deps: [ROOT_STORE] }

(we refer to MyAppState and ROOT_STORE in child module for type safety, but could skip this and use string as a type token if we want complete separation)