[AC-2965] Use OrganizationBillingService to purchase org when FF is on (#4737)

* Add PurchaseSubscription to OrganizationBillingService and call from OrganizationService.SignUpAsync when FF is on

* Run dotnet format

* Missed billing service DI for SCIM which uses the OrganizationService

src/Core/Models/Business/OrganizationSignup.cs

@@ -1,4 +1,5 @@
-using Bit.Core.Entities;
+using Bit.Core.Billing.Models;
+using Bit.Core.Entities;
 using Bit.Core.Enums;
 
 namespace Bit.Core.Models.Business;
@@ -14,4 +15,42 @@ public class OrganizationSignup : OrganizationUpgrade
     public string PaymentToken { get; set; }
     public int? MaxAutoscaleSeats { get; set; } = null;
     public string InitiationPath { get; set; }
+
+    public OrganizationSubscriptionPurchase ToSubscriptionPurchase(bool fromProvider = false)
+    {
+        if (!PaymentMethodType.HasValue)
+        {
+            return null;
+        }
+
+        var metadata = new OrganizationSubscriptionPurchaseMetadata(fromProvider, IsFromSecretsManagerTrial);
+
+        var passwordManager = new OrganizationPasswordManagerSubscriptionPurchase(
+            AdditionalStorageGb,
+            PremiumAccessAddon,
+            AdditionalSeats);
+
+        var paymentSource = new TokenizedPaymentSource(PaymentMethodType.Value, PaymentToken);
+
+        var secretsManager = new OrganizationSecretsManagerSubscriptionPurchase(
+            AdditionalSmSeats ?? 0,
+            AdditionalServiceAccounts ?? 0);
+
+        var taxInformation = new TaxInformation(
+            TaxInfo.BillingAddressCountry,
+            TaxInfo.BillingAddressPostalCode,
+            TaxInfo.TaxIdNumber,
+            TaxInfo.BillingAddressLine1,
+            TaxInfo.BillingAddressLine2,
+            TaxInfo.BillingAddressCity,
+            TaxInfo.BillingAddressState);
+
+        return new OrganizationSubscriptionPurchase(
+            metadata,
+            passwordManager,
+            paymentSource,
+            Plan,
+            UseSecretsManager ? secretsManager : null,
+            taxInformation);
+    }
 }