[PM-6654] new app id service for angular (#8229)

* Improve state documentation

* Add namespace for application id

* Spec out behavior of app id service

* Use state providers for app ids

* Migrate app Id

* Add reactive interface

libs/common/src/platform/abstractions/app-id.service.ts

@@ -1,4 +1,8 @@
+import { Observable } from "rxjs";
+
 export abstract class AppIdService {
+  appId$: Observable<string>;
+  anonymousAppId$: Observable<string>;
   getAppId: () => Promise<string>;
   getAnonymousAppId: () => Promise<string>;
 }