Added Zu-/Abschläge to Delivery Note

Elwig/Models/Delivery.cs

@@ -84,6 +84,17 @@ namespace Elwig.Models {
 
         public string SortIdString => string.Join(", ", SortIds);
 
+        public double Kmw => Parts.Aggregate(
+            (Weight: 0, Kmw: 0.0),
+            (sum, item) => (
+                sum.Weight + item.Weight,
+                (sum.Kmw * sum.Weight + item.Kmw * item.Weight) / (sum.Weight + item.Weight)
+            ),
+            sum => sum.Kmw
+        );
+
+        public double Oe => Utils.KmwToOe(Kmw);
+
         public int SearchScore(IEnumerable<string> keywords) {
             var list = new string?[] {
                 LsNr, Year.ToString(), Date.ToString("dd.MM.yyyy"), Time?.ToString("HH:mm"),