chore: Update variable names for consistency in meal plans service and user registered meal plans service

src/modules/users/modules/meal-plans/services/meal-plans.service.ts

@@ -53,7 +53,7 @@ export class MealPlansService extends CrudService(MealPlan) {
 
         await this.userRegisteredMealPlansService.createForUser(
             {
-                mealPlan: mealPlan._id,
+                meal_plan: mealPlan._id,
             },
             user._id
         );

src/modules/users/modules/user-registered-meal-plans/services/user-registered-meal-plans.service.ts

@@ -20,7 +20,7 @@ export class UserRegisteredMealPlansService extends CrudService(UserRegisteredMe
 
   async createForUser(data: any, userId: string) {
     const mealPlan = await this.mealPlansService.findOneOrFail({
-      _id: data.mealPlan,
+      _id: data.meal_plan,
     });
 
     await this.unregisterCurrentMealPlan(userId);