[AC-1970] Add billing navigation group to provider layout (#8941)

* Add billing navigation item to provider layout with empty subscription page behind FF.

* Fixing tests

* Missed build error

* Addison's feedback

* Remove unused function

* Missed one get$ conversion

* Fixed background failure

libs/common/src/billing/abstractions/provider-billing.service.abstraction.ts

@@ -0,0 +1,25 @@
+import { map, Observable, OperatorFunction, switchMap } from "rxjs";
+
+import { ProviderStatusType } from "@bitwarden/common/admin-console/enums";
+import { Provider } from "@bitwarden/common/admin-console/models/domain/provider";
+import { FeatureFlag } from "@bitwarden/common/enums/feature-flag.enum";
+import { ConfigService } from "@bitwarden/common/platform/abstractions/config/config.service";
+
+type MaybeProvider = Provider | undefined;
+
+export const canAccessBilling = (
+  configService: ConfigService,
+): OperatorFunction<MaybeProvider, boolean> =>
+  switchMap<MaybeProvider, Observable<boolean>>((provider) =>
+    configService
+      .getFeatureFlag$(FeatureFlag.EnableConsolidatedBilling)
+      .pipe(
+        map((consolidatedBillingEnabled) =>
+          provider
+            ? provider.isProviderAdmin &&
+              provider.providerStatus === ProviderStatusType.Billable &&
+              consolidatedBillingEnabled
+            : false,
+        ),
+      ),
+  );