fix : 제목 중복 문제 해결

Author: RTUnu12

src/main/java/com/rtu/chalkac/domain/video/repository/VideoRepository.java

@@ -15,4 +15,6 @@ Page<Video> findByTitleContainingIgnoreCaseOrCategoryNameContainingIgnoreCaseOrU
     );
 
     Page<Video> findByUser(Pageable pageable, Users user);
+
+    boolean existsByTitle(String title);
 }

src/main/java/com/rtu/chalkac/domain/video/service/VideoService.java

@@ -60,6 +60,10 @@ public VideoResponseDto createVideo(CreateVideoRequestDto requestDto) {
         Category category = categoryService.getCategory(Long.parseLong(requestDto.getCategoryId()));
         Users user = usersService.getUser(requestDto.getUserId());
 
+        if(videoRepository.existsByTitle(requestDto.getTitle())) {
+            throw new IllegalArgumentException("Title already exists");
+        }
+
         Video video = Video.builder()
                 .videoId(generateVideoId()) // 별도의 ID 생성 로직 필요
                 .category(category)