Feat: 질문지 종료 메서드 구현

finishDateTime과 값 비교 이후 종료하도록 구현
finishDateTime 이전에 요청이 올 때 반환 될 예외 추가

[#49]

src/main/java/com/careerzip/domain/questionpaper/entity/QuestionPaper.java

@@ -1,6 +1,7 @@
 package com.careerzip.domain.questionpaper.entity;
 
 import com.careerzip.domain.questionpaperform.entity.QuestionPaperForm;
+import com.careerzip.global.error.exception.business.QuestionPaperNotFinishedException;
 import lombok.AccessLevel;
 import lombok.Builder;
 import lombok.Getter;
@@ -49,4 +50,11 @@ private QuestionPaper(Long id, String title, LocalDateTime startDateTime, LocalD
         this.opened = opened;
         this.questionPaperForm = questionPaperForm;
     }
+
+    public void finishPaper() {
+        if (finishDateTime.isAfter(LocalDateTime.now())) {
+            throw new QuestionPaperNotFinishedException();
+        }
+        this.opened = true;
+    }
 }

src/main/java/com/careerzip/global/error/exception/business/QuestionPaperNotFinishedException.java

@@ -0,0 +1,13 @@
+package com.careerzip.global.error.exception.business;
+
+import com.careerzip.global.error.exception.BusinessException;
+import com.careerzip.global.error.response.ErrorCode;
+import lombok.Getter;
+
+@Getter
+public class QuestionPaperNotFinishedException extends BusinessException {
+
+    public QuestionPaperNotFinishedException() {
+        super(ErrorCode.QUESTION_PAPER_NOT_FINISHED);
+    }
+}

src/main/java/com/careerzip/global/error/response/ErrorCode.java

@@ -27,6 +27,7 @@ public enum ErrorCode {
     RECORD_NOT_FOUND(404, "해당 아카이빙 기록을 찾을 수 없습니다."),
 
     // QuestionPaper
+    QUESTION_PAPER_NOT_FINISHED(400, "질문지가 마감되지 않아 종료할 수 없습니다."),
     QUESTION_PAPER_NOT_FOUND(404, "해당 질문지를 찾을 수 없습니다."),
 
     // Project