Displaying NetworkFee if it was present for the invoice

BTCPayServer/Models/InvoicingModels/InvoiceDetailsModel.cs

@@ -22,6 +22,8 @@ namespace BTCPayServer.Models.InvoicingModels
         public bool Replaced { get; set; }
         public BitcoinLikePaymentData CryptoPaymentData { get; set; }
         public string AdditionalInformation { get; set; }
+
+        public decimal NetworkFee { get; set; }
     }
 
     public class OffChainPaymentViewModel