[AC-2805] Add AssignedSeats to ProviderOrganizationOrganizationDetailsView (#4446)

* Add 'AssignedSeats' to ProviderOrganizationOrganizationDetailsView

* Add newline

* Thomas' feedback

src/Core/AdminConsole/Models/Data/Provider/ProviderOrganizationOrganizationDetails.cs

@@ -20,6 +20,7 @@ public class ProviderOrganizationOrganizationDetails
     public DateTime CreationDate { get; set; }
     public DateTime RevisionDate { get; set; }
     public int UserCount { get; set; }
+    public int? OccupiedSeats { get; set; }
     public int? Seats { get; set; }
     public string Plan { get; set; }
     public OrganizationStatusType Status { get; set; }