[Feat] 이해도 체크 생성 API 구현

backend/src/main/java/com/example/Piroin/project/domain/curriculum/repository/CurriculumRepository.java

@@ -11,7 +11,7 @@
 Q&A 서비스에서 세션 존재 여부 확인 시 사용
 JpaRepository<엔티티 타입, PK 타입> 을 상속하면 findById, save, delete 등 기본 메서드가 자동으로 제공
 */
-public interface CurriculumRepository extends JpaRepository<StudySession, Integer> {
+public interface CurriculumRepository extends JpaRepository<StudySession, Long> {
     List<StudySession> findByStatusOrderBySessionDateAscDayPartAsc(SessionStatus status);
 
     List<StudySession> findByStatusOrderBySessionDateDescDayPartDesc(SessionStatus status);

backend/src/main/java/com/example/Piroin/project/domain/curriculum/service/CurriculumService.java

@@ -50,7 +50,7 @@ public CurriculumResDTO.CreateSessionRes createSession(CurriculumReqDTO.CreateSe
 
     @Transactional
     public CurriculumResDTO.UpdateSessionRes updateSession(Long sessionId, CurriculumReqDTO.UpdateSessionReq req) {
-        StudySession session = curriculumRepository.findById(Math.toIntExact(sessionId))
+        StudySession session = curriculumRepository.findById(sessionId)
                 .orElseThrow(() -> new CurriculumException(HttpStatus.NOT_FOUND, "세션을 찾을 수 없습니다."));
 
         session.update(req.getGeneration(), req.getWeek(), req.getSessionDate(), req.getDayPart(),
@@ -63,7 +63,7 @@ public CurriculumResDTO.UpdateSessionRes updateSession(Long sessionId, Curriculu
 
     @Transactional
     public void deleteSession(Long sessionId) {
-        StudySession session = curriculumRepository.findById(Math.toIntExact(sessionId))
+        StudySession session = curriculumRepository.findById(sessionId)
                 .orElseThrow(() -> new CurriculumException(HttpStatus.NOT_FOUND, "세션을 찾을 수 없습니다."));
 
         curriculumRepository.delete(session);

backend/src/main/java/com/example/Piroin/project/domain/question/controller/QuestionController.java

@@ -73,6 +73,18 @@ public ResponseEntity<ApiResponse<QuestionResDTO.LikeRes>> toggleLike(
                 questionService.toggleLike(questionId, userId));
     }
 
+    // 이해도 체크 생성
+    // POST /api/sessions/{sessionId}/understanding-checks
+    @PostMapping("/api/sessions/{sessionId}/understanding-checks")
+    public ResponseEntity<ApiResponse<QuestionResDTO.UnderstandingCheckCreateResponse>> createUnderstandingCheck(
+            @PathVariable Long sessionId,
+            @RequestBody QuestionReqDTO.UnderstandingCheckCreateReq request,
+            @AuthenticationPrincipal Long userId
+    ) {
+        return ResponseUtil.success(QuestionSuccessCode.UNDERSTANDING_CHECK_CREATED,
+                questionService.createUnderstandingCheck(sessionId, request, userId));
+    }
+
     // 이해도 체크 응답
     // POST /api/sessions/{sessionId}/understanding-checks/{checkId}/responses
     @PostMapping("/api/sessions/{sessionId}/understanding-checks/{checkId}/responses")

backend/src/main/java/com/example/Piroin/project/domain/question/dto/QuestionReqDTO.java

@@ -28,4 +28,11 @@ public static class CommentReq {
     public static class UnderstandingResponseReq {
         private UnderstandResChoice choice;
     }
+
+    // 이해도 체크 생성 요청
+    @Getter
+    @NoArgsConstructor
+    public static class UnderstandingCheckCreateReq {
+        private String content;
+    }
 }

backend/src/main/java/com/example/Piroin/project/domain/question/dto/QuestionResDTO.java

@@ -105,8 +105,7 @@ public record UnderstandingSliceResponse(
 
     public record UnderstandingCheckResponse(
             Long checkId,
-            String title,
-            String description,
+            String content,
             Integer understoodCount,
             Integer notUnderstoodCount,
             LocalDateTime createdAt
@@ -139,4 +138,13 @@ public record UnderstandingResponseResult(
             Integer notUnderstoodCount
     ) {
     }
+
+    public record UnderstandingCheckCreateResponse(
+            Long checkId,
+            String content,
+            Integer understoodCount,
+            Integer notUnderstoodCount,
+            LocalDateTime createdAt
+    ) {
+    }
 }

backend/src/main/java/com/example/Piroin/project/domain/question/exception/code/QuestionSuccessCode.java

@@ -14,7 +14,8 @@ public enum QuestionSuccessCode implements BaseCode {
     LIKE_TOGGLED(HttpStatus.OK, "QUESTION200_3", "좋아요가 처리되었습니다."),          // ← 추가
     UNDERSTANDING_RESPONSE_OK(HttpStatus.OK, "QUESTION200_4", "이해도 응답이 반영되었습니다."),
     QUESTION_CREATED(HttpStatus.CREATED, "QUESTION201_1", "질문이 등록되었습니다."),
-    COMMENT_CREATED(HttpStatus.CREATED, "QUESTION201_2", "댓글이 등록되었습니다.");
+    COMMENT_CREATED(HttpStatus.CREATED, "QUESTION201_2", "댓글이 등록되었습니다."),
+    UNDERSTANDING_CHECK_CREATED(HttpStatus.CREATED, "QUESTION201_3", "이해도 체크가 생성되었습니다.");
 
     private final HttpStatus status;
     private final String code;

backend/src/main/java/com/example/Piroin/project/domain/question/service/QuestionService.java

@@ -237,6 +237,30 @@ public QuestionResDTO.LikeRes toggleLike(Long questionId, Long userId) {
                 });
     }
 
+    // 이해도 체크 생성
+    @Transactional
+    public QuestionResDTO.UnderstandingCheckCreateResponse createUnderstandingCheck(
+            Long sessionId, QuestionReqDTO.UnderstandingCheckCreateReq request, Long userId
+    ) {
+        validateUnderstandingCheckCreateRequest(request);
+        User loginUser = findLoginUser(userId);
+        validateAdmin(loginUser);
+        StudySession session = findSession(sessionId);
+
+        LocalDateTime now = LocalDateTime.now();
+        UnderstandingCheck check = understandingCheckRepository.save(UnderstandingCheck.builder()
+                .session(session)
+                .createdBy(loginUser)
+                .title(request.getContent().trim())
+                .createdAt(now)
+                .updatedAt(now)
+                .build());
+
+        return new QuestionResDTO.UnderstandingCheckCreateResponse(
+                check.getId(), check.getTitle(), 0, 0, check.getCreatedAt()
+        );
+    }
+
     // 이해도 체크 응답
     @Transactional
     public QuestionResDTO.UnderstandingResponseResult respondUnderstandingCheck(
@@ -263,13 +287,25 @@ private User findLoginUser(Long userId) {
                 .orElseThrow(() -> new QuestionException(HttpStatus.UNAUTHORIZED, "로그인 사용자를 찾을 수 없습니다."));
     }
 
+    private void validateAdmin(User loginUser) {
+        if (loginUser.getRole() != Role.ADMIN) {
+            throw new QuestionException(HttpStatus.FORBIDDEN, "관리자만 이해도 체크를 생성할 수 있습니다.");
+        }
+    }
+
+    private void validateUnderstandingCheckCreateRequest(QuestionReqDTO.UnderstandingCheckCreateReq request) {
+        if (request == null || request.getContent() == null || request.getContent().isBlank()) {
+            throw new IllegalArgumentException("이해도 체크 내용은 필수입니다.");
+        }
+    }
+
     private Question findQuestion(Long questionId) {
         return questionRepository.findByIdAndDeletedAtIsNull(questionId)
                 .orElseThrow(() -> new QuestionException(HttpStatus.NOT_FOUND, "질문을 찾을 수 없습니다."));
     }
 
     private StudySession findSession(Long sessionId) {
-        return curriculumRepository.findById(Math.toIntExact(sessionId))
+        return curriculumRepository.findById(sessionId)
                 .orElseThrow(() -> new QuestionException(HttpStatus.NOT_FOUND, "세션을 찾을 수 없습니다."));
     }
 
@@ -346,7 +382,7 @@ private QuestionResDTO.UnderstandingSliceResponse getUnderstandingSlice(StudySes
 
     private QuestionResDTO.UnderstandingCheckResponse toUnderstandingCheckResponse(UnderstandingCheck check) {
         return new QuestionResDTO.UnderstandingCheckResponse(
-                check.getId(), check.getTitle(), check.getDescription(),
+                check.getId(), check.getTitle(),
                 understandingResponseRepository.countByCheckAndChoice(check, UnderstandResChoice.UNDERSTOOD),
                 understandingResponseRepository.countByCheckAndChoice(check, UnderstandResChoice.NOT_UNDERSTOOD),
                 check.getCreatedAt()

backend/src/main/java/com/example/Piroin/project/global/config/SecurityConfig.java

@@ -39,6 +39,9 @@ public SecurityFilterChain filterChain(HttpSecurity http) throws Exception {
                         .requestMatchers(HttpMethod.PATCH, "/api/curriculums/{id}").hasRole("ADMIN")
                         .requestMatchers(HttpMethod.DELETE, "/api/curriculums/{id}").hasRole("ADMIN")
 
+                        // understanding check: 생성은 ADMIN만 가능
+                        .requestMatchers(HttpMethod.POST, "/api/sessions/{sessionId}/understanding-checks").hasRole("ADMIN")
+
                         // Swagger
                         .requestMatchers(
                                 "/swagger-ui/**",