[PM-11404] Account Management: Prevent a verified user from purging their vault (#4853)

* Add check for managed user before purging account

* Rename IOrganizationRepository.GetByClaimedUserDomainAsync to GetByVerifiedUserEmailDomainAsync and refactor to return a list. Remove ManagedByOrganizationId from ProfileResponseMode. Add ManagesActiveUser to ProfileOrganizationResponseModel

* Rename the property ManagesActiveUser to UserIsManagedByOrganization

* Remove whole class #nullable enable and add it to specific places

* Remove unnecessary .ToList()

* Refactor IUserService methods GetOrganizationsManagingUserAsync and IsManagedByAnyOrganizationAsync to not return nullable objects. Update ProfileOrganizationResponseModel.UserIsManagedByOrganization to not be nullable

* Update error message when unable to purge vault for managed account

src/Core/Services/IUserService.cs

@@ -90,14 +90,20 @@ public interface IUserService
     /// Indicates if the user is managed by any organization.
     /// </summary>
     /// <remarks>
-    /// A managed user is a user whose email domain matches one of the Organization's verified domains.
-    /// The organization must be enabled and be on an Enterprise plan.
+    /// A user is considered managed by an organization if their email domain matches one of the verified domains of that organization, and the user is a member of it.
+    /// The organization must be enabled and able to have verified domains.
     /// </remarks>
+    /// <returns>
+    /// False if the Account Deprovisioning feature flag is disabled.
+    /// </returns>
     Task<bool> IsManagedByAnyOrganizationAsync(Guid userId);
 
     /// <summary>
-    /// Gets the organization that manages the user.
+    /// Gets the organizations that manage the user.
     /// </summary>
+    /// <returns>
+    /// An empty collection if the Account Deprovisioning feature flag is disabled.
+    /// </returns>
     /// <inheritdoc cref="IsManagedByAnyOrganizationAsync(Guid)"/>
-    Task<Organization> GetOrganizationManagingUserAsync(Guid userId);
+    Task<IEnumerable<Organization>> GetOrganizationsManagingUserAsync(Guid userId);
 }