feat: 마이바(MyBar) '킵' 기능 추가 및 목록 조회 로직 개선

- `keep` 메서드를 추가하여 칵테일을 킵하거나 재킵하는 로직 구현
- 기존 목록 조회 메서드(`getMyBar`)의 쿼리 정렬 기준을 `KeptAt`으로 변경
- `UserRepository`와 `CocktailRepository`를 추가하여 엔티티 참조에 활용

Author: MEOHIN

src/main/java/com/back/domain/mybar/service/MyBarService.java

@@ -1,28 +1,34 @@
 package com.back.domain.mybar.service;
 
+import com.back.domain.cocktail.repository.CocktailRepository;
 import com.back.domain.mybar.dto.MyBarItemResponseDto;
 import com.back.domain.mybar.dto.MyBarListResponseDto;
 import com.back.domain.mybar.entity.MyBar;
 import com.back.domain.mybar.enums.KeepStatus;
 import com.back.domain.mybar.repository.MyBarRepository;
+import com.back.domain.user.repository.UserRepository;
 import lombok.RequiredArgsConstructor;
 import org.springframework.data.domain.Page;
 import org.springframework.data.domain.PageRequest;
 import org.springframework.stereotype.Service;
 import org.springframework.transaction.annotation.Transactional;
 
+import java.time.LocalDateTime;
 import java.util.ArrayList;
 import java.util.List;
+import java.util.Optional;
 
 @Service
 @RequiredArgsConstructor
 public class MyBarService {
 
     private final MyBarRepository myBarRepository;
+    private final UserRepository userRepository;
+    private final CocktailRepository cocktailRepository;
 
     @Transactional(readOnly = true)
     public MyBarListResponseDto getMyBar(Long userId, int page, int pageSize) {
-        Page<MyBar> myBarPage = myBarRepository.findByUserIdAndStatusOrderByIdDesc(userId, KeepStatus.ACTIVE, PageRequest.of(page, pageSize));
+        Page<MyBar> myBarPage = myBarRepository.findByUser_IdAndStatusOrderByKeptAtDescIdDesc(userId, KeepStatus.ACTIVE, PageRequest.of(page, pageSize));
 
         List<MyBar> myBars = myBarPage.getContent();
         List<MyBarItemResponseDto> items = new ArrayList<>();
@@ -33,4 +39,33 @@ public MyBarListResponseDto getMyBar(Long userId, int page, int pageSize) {
 
         return new MyBarListResponseDto(items, hasNext, nextPage);
     }
+
+    @Transactional
+    public void keep(Long userId, Long cocktailId) {
+        Optional<MyBar> existingMyBar =
+                myBarRepository.findByUser_IdAndCocktail_Id(userId, cocktailId);
+
+        LocalDateTime now = LocalDateTime.now();
+
+        if (existingMyBar.isPresent()) {
+            // 이미 행이 있으면: 최근에 다시 킵했다고 보고 keptAt만 갱신
+            MyBar myBar = existingMyBar.get();
+            myBar.setKeptAt(now);
+            if (myBar.getStatus() == KeepStatus.DELETED) {
+                // 해제돼 있던 건 복원
+                myBar.setStatus(KeepStatus.ACTIVE);
+                myBar.setDeletedAt(null);
+            }
+            return; // 이미 ACTIVE여도 keptAt 갱신으로 충분
+        }
+
+        // 없으면 새로 생성
+        MyBar myBar = new MyBar();
+        myBar.setUser(userRepository.getReferenceById(userId));
+        myBar.setCocktail(cocktailRepository.getReferenceById(cocktailId));
+        myBar.setStatus(KeepStatus.ACTIVE);
+        myBar.setKeptAt(now);
+
+        myBarRepository.save(myBar);
+    }
 }