fix(state stream): ensure state property is always updated

Using `reducedState$.subscribe(this.subject)` works fine in all our tests, but when trying
to use StateStream in ardoq-front I ran into issues with the `.state` property not being
updated. I have not managed to write a test to verify this behavior, but manually creating
an Observer fixed the issue.

src/persistentReducedStream.spec.ts

@@ -7,6 +7,9 @@ import { never, of, Subject } from 'rxjs';
 import { marbles } from 'rxjs-marbles/ava';
 import { incrementMocks } from './internal/testing/mock';
 import { map } from 'rxjs/operators';
+import { reducer } from './reducer';
+import { actionCreator } from './actionCreator';
+import { UnknownAction } from './internal';
 
 const { reducers, actionCreators, handlers } = incrementMocks;
 const { actions, numbers, errors } = incrementMocks.marbles;

src/persistentReducedStream.ts

@@ -25,7 +25,15 @@ export class StateStream<State> extends Observable<State>
   constructor(initialState: State, reducedState$: Observable<State>) {
     super();
     this.subject = new BehaviorSubject(initialState);
-    this.subscription = reducedState$.subscribe(this.subject);
+
+    // NOTE: .subscribe(this.subject) does not work
+    // All tests pass with it, but in practice there are cases
+    // where the subject isn't updated as expected
+    this.subscription = reducedState$.subscribe({
+      complete: () => this.subject.complete(),
+      error: (err) => this.subject.error(err),
+      next: (state) => this.subject.next(state),
+    });
   }
 
   get state(): State {