added provider for recipe wizard

lib/models/recipe.dart

@@ -6,26 +6,67 @@ class Recipe {
   final String title;
   final String description;
   final Difficulty difficulty;
-  final List<IngredientListEntry> ingredients = [];
-  final List<String> steps = [];
+  final List<IngredientListEntry> ingredients;
+  final List<String> steps;
   final DateTime datePublished;
   final Duration prepTime;
   final Duration cookTime;
   final Duration totalTime;
-  final List<String> keywords = [];
+  final List<String> keywords;
   final MealCategory mealCategory;
   final Cuisine cuisine;
 
   Recipe({
-    required this.id,
-    required this.title,
-    required this.description,
-    required this.difficulty,
+    this.id = -1,
+    this.title = '',
+    this.description = '',
+    this.difficulty = Difficulty.notSelected,
     required this.datePublished,
-    required this.prepTime,
-    required this.cookTime,
-    required this.totalTime,
-    required this.mealCategory,
-    required this.cuisine,
+    this.prepTime = const Duration(),
+    this.cookTime = const Duration(),
+    this.totalTime = const Duration(),
+    this.mealCategory = MealCategory.notSelected,
+    this.cuisine = Cuisine.notSelected,
+    this.ingredients = const [],
+    this.keywords = const [],
+    this.steps = const [],
   });
+
+  Recipe copyWith({
+    int? id,
+    String? title,
+    String? description,
+    Difficulty? difficulty,
+    List<IngredientListEntry>? ingredients,
+    List<String>? steps,
+    DateTime? datePublished,
+    Duration? prepTime,
+    Duration? cookTime,
+    Duration? totalTime,
+    List<String>? keywords,
+    MealCategory? mealCategory,
+    Cuisine? cuisine,
+  }) {
+    return Recipe(
+      id: id ?? this.id,
+      title: title ?? this.title,
+      description: description ?? this.description,
+      difficulty: difficulty ?? this.difficulty,
+      ingredients: ingredients != null
+          ? List<IngredientListEntry>.from(ingredients)
+          : List<IngredientListEntry>.from(this.ingredients),
+      steps: steps != null
+          ? List<String>.from(steps)
+          : List<String>.from(this.steps),
+      datePublished: datePublished ?? this.datePublished,
+      prepTime: prepTime ?? this.prepTime,
+      cookTime: cookTime ?? this.cookTime,
+      totalTime: totalTime ?? this.totalTime,
+      keywords: keywords != null
+          ? List<String>.from(keywords)
+          : List<String>.from(this.keywords),
+      mealCategory: mealCategory ?? this.mealCategory,
+      cuisine: cuisine ?? this.cuisine,
+    );
+  }
 }