[PM-21821] Provider portal takeover states (#6109)

* Add feature flag

* Disable provider and schedule cancellation when subscription goes unpaid

* Run dotnet format

* Only set provider subscription cancel_at when subscription is going from paid to unpaid

* Update tests

src/Billing/Startup.cs

@@ -5,6 +5,7 @@ using System.Globalization;
 using System.Net.Http.Headers;
 using Bit.Billing.Services;
 using Bit.Billing.Services.Implementations;
+using Bit.Commercial.Core.Utilities;
 using Bit.Core.Billing.Extensions;
 using Bit.Core.Context;
 using Bit.Core.SecretsManager.Repositories;
@@ -83,6 +84,7 @@ public class Startup
         services.AddDefaultServices(globalSettings);
         services.AddDistributedCache(globalSettings);
         services.AddBillingOperations();
+        services.AddCommercialCoreServices();
 
         services.TryAddSingleton<IHttpContextAccessor, HttpContextAccessor>();