[feat] 스터디 가입 요청, 수락, 거절 API 추가

src/main/java/com/flytrap/venusplanner/api/join_request/business/service/JoinRequestCurdFacadeService.java

@@ -75,4 +75,30 @@ public void acceptJoinRequest(Long studyId, Long requestId, Long memberId) {
         joinRequest.accept();
     }
 
+    @Transactional
+    public void rejectJoinRequest(Long studyId, Long requestId, Long memberId) {
+        if (!studyRepository.existsById(studyId)) {
+            throw new StudyNotFoundException("스터디를 찾을 수 없습니다.");
+        }
+
+        MemberStudy memberStudy = memberStudyRepository.findByStudyIdAndMemberId(studyId, memberId)
+                .orElseThrow(() -> new ForbiddenException("스터디 멤버가 아닙니다."));
+
+        if (!memberStudy.isLeader()) {
+            throw new ForbiddenException("수락 권한이 없습니다.");
+        }
+
+        JoinRequest joinRequest = joinRequestRepository.findById(requestId)
+                .orElseThrow(() -> new JoinRequestNotFoundException("JoinRequest를 찾을 수 없습니다."));
+
+        if (!joinRequest.validateStudyIdMatch(studyId)) {
+            throw new StudyMismatchException("요청한 스터디 ID와 가입 요청의 스터디 ID가 일치하지 않습니다");
+        }
+
+        if (!joinRequest.isWaiting()) {
+            throw new JoinRequestAlreadyHandledException("이미 처리된 요청입니다.");
+        }
+        joinRequest.reject();
+    }
+
 }

src/main/java/com/flytrap/venusplanner/api/join_request/domain/JoinRequest.java

@@ -62,8 +62,12 @@ public boolean accept() {
         return true;
     }
 
-    public void reject() {
-
+    public boolean reject() {
+        if (!isWaiting()) {
+            return false;
+        }
+        this.state = JoinRequestState.REJECT;
+        return true;
     }
 
 }

src/main/java/com/flytrap/venusplanner/api/join_request/presentation/controller/JoinRequestController.java

@@ -42,4 +42,15 @@ public ResponseEntity<Void> acceptJoinRequest(
         return ResponseEntity.ok(null);
     }
 
+    @PatchMapping("/api/v1/studies/{studyId}/join-requests/{requestId}/reject")
+    public ResponseEntity<Void> rejectJoinRequest(
+            @PathVariable Long studyId,
+            @PathVariable Long requestId,
+            @SignIn SessionMember sessionMember
+    ) {
+        joinRequestCrudService.rejectJoinRequest(studyId, requestId, sessionMember.id());
+
+        return ResponseEntity.ok(null);
+    }
+
 }