Billing: Add feature to calculate member/delivery bins

Elwig/Helpers/Utils.cs

@@ -326,5 +326,19 @@ namespace Elwig.Helpers {
                 return (familyName, fullName.Replace(familyName, "").Replace("  ", " ").Trim());
             }
         }
+
+        public static IEnumerable<IEnumerable<T>> Permutate<T>(IEnumerable<T> input) {
+            List<IEnumerable<T>> output = new();
+            for (int i = 0; i < Math.Pow(2, input.Count()); i++) {
+                List<T> t = new();
+                for (int j = 0; j < 30; j++) {
+                    if ((i & (1 << j)) != 0) {
+                        t.Add(input.ElementAt(j));
+                    }
+                }
+                output.Add(t);
+            }
+            return output.OrderByDescending(l => l.Count());
+        }
     }
 }