ability to display added ingredients in listview

lib/models/ingredient.dart

@@ -7,7 +7,7 @@ class Ingredient {
 
   Ingredient({
     required this.title,
-    required this.possibleUnits,
+    this.possibleUnits = const [],
     this.preferredBrands = const [],
   });
 

lib/models/ingredient_list_entry.dart

@@ -0,0 +1,11 @@
+import 'ingredient.dart';
+import 'unit.dart';
+
+class IngredientListEntry {
+  final Ingredient ingredient;
+  final int amount;
+  final Unit unit;
+  final bool optional;
+
+  IngredientListEntry(this.ingredient, this.amount, this.unit, this.optional);
+}