feat: limit the number of comments a user can create

Author: lkw9241

src/main/java/com/back/domain/cocktail/comment/entity/CocktailComment.java

@@ -15,6 +15,10 @@
 import java.time.LocalDateTime;
 
 @Entity
+@Table(
+        name = "cocktail_comment",
+        uniqueConstraints = @UniqueConstraint(columnNames = {"cocktail_id", "user_id"}) // 사용자 1개 댓글 제한
+)
 @Getter
 @EntityListeners(AuditingEntityListener.class)
 @NoArgsConstructor(access = lombok.AccessLevel.PROTECTED)

src/main/java/com/back/domain/cocktail/comment/repository/CocktailCommentRepository.java

@@ -12,4 +12,6 @@ public interface CocktailCommentRepository extends JpaRepository<CocktailComment
     List<CocktailComment> findTop10ByCocktailIdOrderByIdDesc(Long cocktailId);
 
     List<CocktailComment> findTop10ByCocktailIdAndIdLessThanOrderByIdDesc(Long cocktailId, Long lastId);
+
+    boolean existsByCocktailIdAndUserId(Long cocktailId, Long id);
 }

src/main/java/com/back/domain/cocktail/comment/service/CocktailCommentService.java

@@ -31,6 +31,12 @@ public CocktailCommentResponseDto createCocktailComment(Long cocktailId, Cocktai
         Cocktail cocktail = cocktailRepository.findById(cocktailId)
                 .orElseThrow(() -> new IllegalArgumentException("칵테일이 존재하지 않습니다. id=" + cocktailId));
 
+        // 사용자당 댓글 1개 제한 체크
+        boolean exists = cocktailCommentRepository.existsByCocktailIdAndUserId(cocktailId, user.getId());
+        if (exists) {
+            throw new IllegalArgumentException("이미 댓글을 작성하셨습니다.");
+        }
+
         CocktailComment cocktailComment = CocktailComment.builder()
                 .cocktail(cocktail)
                 .user(user)