[PM-18770] Convert Organization to Business Unit (#5610)

* [NO LOGIC] Rename MultiOrganizationEnterprise to BusinessUnit

* [Core] Add IMailService.SendBusinessUnitConversionInviteAsync

* [Core] Add BusinessUnitConverter

* [Admin] Add new permission

* [Admin] Add BusinessUnitConverterController

* [Admin] Add Convert to Business Unit button to Organization edit page

* [Api] Add OrganizationBillingController.SetupBusinessUnitAsync action

* [Multi] Propagate provider type to sync response

* [Multi] Put updates behind feature flag

* [Tests] BusinessUnitConverterTests

* Run dotnet format

* Fixing post-main merge compilation failure

src/Core/Billing/Extensions/BillingExtensions.cs

@@ -25,19 +25,19 @@ public static class BillingExtensions
     public static bool IsBillable(this Provider provider) =>
         provider is
         {
-            Type: ProviderType.Msp or ProviderType.MultiOrganizationEnterprise,
+            Type: ProviderType.Msp or ProviderType.BusinessUnit,
             Status: ProviderStatusType.Billable
         };
 
     public static bool IsBillable(this InviteOrganizationProvider inviteOrganizationProvider) =>
         inviteOrganizationProvider is
         {
-            Type: ProviderType.Msp or ProviderType.MultiOrganizationEnterprise,
+            Type: ProviderType.Msp or ProviderType.BusinessUnit,
             Status: ProviderStatusType.Billable
         };
 
     public static bool SupportsConsolidatedBilling(this ProviderType providerType)
-        => providerType is ProviderType.Msp or ProviderType.MultiOrganizationEnterprise;
+        => providerType is ProviderType.Msp or ProviderType.BusinessUnit;
 
     public static bool IsValidClient(this Organization organization)
         => organization is

src/Core/Billing/Services/IBusinessUnitConverter.cs

@@ -0,0 +1,58 @@
+using Bit.Core.AdminConsole.Entities;
+using Bit.Core.AdminConsole.Entities.Provider;
+using Bit.Core.AdminConsole.Enums.Provider;
+using OneOf;
+
+namespace Bit.Core.Billing.Services;
+
+public interface IBusinessUnitConverter
+{
+    /// <summary>
+    /// Finalizes the process of converting the <paramref name="organization"/> to a <see cref="ProviderType.BusinessUnit"/> by
+    /// saving all the necessary key provided by the client and updating the <paramref name="organization"/>'s subscription to a
+    /// provider subscription.
+    /// </summary>
+    /// <param name="organization">The organization to convert to a business unit.</param>
+    /// <param name="userId">The ID of the organization member who will be the provider admin.</param>
+    /// <param name="token">The token sent to the client as part of the <see cref="InitiateConversion"/> process.</param>
+    /// <param name="providerKey">The encrypted provider key used to enable the <see cref="ProviderUser"/>.</param>
+    /// <param name="organizationKey">The encrypted organization key used to enable the <see cref="ProviderOrganization"/>.</param>
+    /// <returns>The provider ID</returns>
+    Task<Guid> FinalizeConversion(
+        Organization organization,
+        Guid userId,
+        string token,
+        string providerKey,
+        string organizationKey);
+
+    /// <summary>
+    /// Begins the process of converting the <paramref name="organization"/> to a <see cref="ProviderType.BusinessUnit"/> by
+    /// creating all the necessary database entities and sending a setup invitation to the <paramref name="providerAdminEmail"/>.
+    /// </summary>
+    /// <param name="organization">The organization to convert to a business unit.</param>
+    /// <param name="providerAdminEmail">The email address of the organization member who will be the provider admin.</param>
+    /// <returns>Either the newly created provider ID or a list of validation failures.</returns>
+    Task<OneOf<Guid, List<string>>> InitiateConversion(
+        Organization organization,
+        string providerAdminEmail);
+
+    /// <summary>
+    /// Checks if the <paramref name="organization"/> has a business unit conversion in progress and, if it does, resends the
+    /// setup invitation to the provider admin.
+    /// </summary>
+    /// <param name="organization">The organization to convert to a business unit.</param>
+    /// <param name="providerAdminEmail">The email address of the organization member who will be the provider admin.</param>
+    Task ResendConversionInvite(
+        Organization organization,
+        string providerAdminEmail);
+
+    /// <summary>
+    /// Checks if the <paramref name="organization"/> has a business unit conversion in progress and, if it does, resets that conversion
+    /// by deleting all the database entities created as part of <see cref="InitiateConversion"/>.
+    /// </summary>
+    /// <param name="organization">The organization to convert to a business unit.</param>
+    /// <param name="providerAdminEmail">The email address of the organization member who will be the provider admin.</param>
+    Task ResetConversion(
+        Organization organization,
+        string providerAdminEmail);
+}