[AC-1910] Allocate seats to a provider organization (#3936)

* Add endpoint to update a provider organization's seats for consolidated billing.

* Fixed failing tests

src/Api/Startup.cs

@@ -170,8 +170,7 @@ public class Startup
         services.AddDefaultServices(globalSettings);
         services.AddOrganizationSubscriptionServices();
         services.AddCoreLocalizationServices();
-        services.AddBillingCommands();
-        services.AddBillingQueries();
+        services.AddBillingOperations();
 
         // Authorization Handlers
         services.AddAuthorizationHandlers();