Add procurement domain models (PurchaseOrder, GoodsReceipt, PurchaseReturn)

Distribution/Models/PurchaseOrder.cs

@@ -0,0 +1,19 @@
+using System.ComponentModel.DataAnnotations.Schema;
+
+namespace Distribution.Models
+{
+    public class PurchaseOrder : Template
+    {
+        public Guid FK_SupplierId { get; set; }
+        [ForeignKey("FK_SupplierId")]
+        public Supplier Supplier { get; set; }
+
+        public Guid FK_CreatedByUserId { get; set; }
+
+        public PurchaseOrderStatus Status { get; set; } = PurchaseOrderStatus.Issued;
+
+        public string? CancelReason { get; set; }
+
+        public ICollection<PurchaseOrderItem> Items { get; set; } = [];
+    }
+}