Add returns and claims

Distribution/Models/CreditNote.cs

@@ -0,0 +1,15 @@
+using System.ComponentModel.DataAnnotations.Schema;
+
+namespace Distribution.Models
+{
+    /// <summary>Audit record of the credit amount netted off an order by a CreditDeduction-mode SaleReturn.</summary>
+    public class CreditNote : Template
+    {
+        public Guid FK_SaleReturnId { get; set; }
+        [ForeignKey("FK_SaleReturnId")]
+        public SaleReturn SaleReturn { get; set; }
+
+        public decimal Amount { get; set; }
+        public DateTime IssuedAt { get; set; } = DateTime.Now;
+    }
+}