[#19]Feat : Create DishService

- DishService 생성 및 테스트 코드 추가

backend/src/main/java/com/team15/sidedish/service/DishService.java

@@ -0,0 +1,32 @@
+package com.team15.sidedish.service;
+
+import com.team15.sidedish.domain.Dish;
+import com.team15.sidedish.domain.DishRepository;
+import org.springframework.stereotype.Service;
+
+import java.security.PublicKey;
+import java.util.List;
+
+@Service
+public class DishService {
+    private final DishRepository dishRepository;
+
+    public DishService(DishRepository dishRepository) {
+        this.dishRepository = dishRepository;
+    }
+
+    public List<Dish> showDishes() {
+        List<Dish> dishes = (List<Dish>) dishRepository.findAll();
+        return dishes;
+    }
+
+    public Dish showSingleDish(String hash) {
+        Dish dish = dishRepository.findById(hash).get();
+        return dish;
+    }
+
+//    public List<Dish> showDishesBySectionName(String sectionName) {
+//        return dishRepository.findAllBySectionName(sectionName);
+//    }
+
+}