changes to recipe class and providers

lib/models/recipe.dart

@@ -6,12 +6,31 @@ class Recipe {
   final String title;
   final String description;
   final Difficulty? difficulty;
-  final List<IngredientListEntry> ingredients = [];
-  final List<CookingStep> steps = [];
+  final List<IngredientListEntry> ingredients;
+  final List<CookingStep> steps;
 
   Recipe({
     required this.title,
     this.description = '',
     this.difficulty,
+    this.ingredients = const [],
+    this.steps = const [],
   });
+
+  void addIngredient(IngredientListEntry ingredient) =>
+      ingredients.add(ingredient);
+
+  void clearIngredients() => ingredients.clear();
+
+  void removeIngredientAt(int index) {
+    ingredients.removeAt(index);
+  }
+
+  void removeIngredient(IngredientListEntry ingredient) {
+    ingredients.removeWhere((element) => element == ingredient);
+  }
+
+  void addStep(CookingStep step) => steps.add(step);
+
+  void removeStepAt(int index) => steps.removeAt(index);
 }