add feature for users to create and store recipes

backend/models/Recipe.js

@@ -55,6 +55,11 @@ const recipeSchema = new mongoose.Schema({
     type: String,
     default: ''
   },
+  createdBy: {
+    type: mongoose.Schema.Types.ObjectId,
+    ref: 'User',
+    required: true
+  },
   createdAt: {
     type: Date,
     default: Date.now