Billing: Rename attributeVariants and contracts to vaributes

Elwig/Helpers/Billing/Varibute.cs

@@ -0,0 +1,25 @@
+using Elwig.Models.Entities;
+using System;
+
+namespace Elwig.Helpers.Billing {
+    public class Varibute : IComparable<Varibute> {
+
+        public WineVar? Variety { get; }
+        public WineAttr? Attribute { get; }
+        public string Listing => $"{Variety?.SortId}{Attribute?.AttrId}";
+        public string FullName => $"{Variety?.Name}" + (Variety != null && Attribute != null ? " " : "") + $"{Attribute?.Name}";
+
+        public Varibute(WineVar? var, WineAttr? attr) {
+            Variety = var;
+            Attribute = attr;
+        }
+
+        public override string ToString() {
+            return Listing;
+        }
+
+        public int CompareTo(Varibute? other) {
+            return Listing.CompareTo(other?.Listing);
+        } 
+    }
+}