Billing: Add functionality to collapse curves

Elwig/Models/Entities/WineVar.cs

@@ -21,6 +21,13 @@ namespace Elwig.Models.Entities {
         public bool IsRed => Type == "R";
         public bool IsWhite => Type == "W";
 
+        public WineVar() { }
+
+        public WineVar(string sortId, string name) {
+            SortId = sortId;
+            Name = name;
+        }
+
         public override string ToString() {
             return Name;
         }