[Server] 댓글 작성

#제목에 [Client], [Server] 꼭 써주세요!
#Labels 꼭 추가해야하는 라벨!
Type: feature, bug
Estimated time(예상소요시간) : 1h
Urgency(버그 중요도) : High, Middle, Low (버그있을때만 라벨넣어주시면 됩니다!)

###TODO 최대한 세세하게 써주세요!
- [ ] 댓글 내용, 작성자, 작성날짜 DB에 삽입 (comment table - foreign key 확인)
- [ ] 성공 실패시 응답

###Estimated time
> 하나를 골라주세요! 라벨만 추가해주시면 됩니다~!~!
- 0.5h
- 1h
- 1.5h
- 2h
- 2.5h
- 3h

Start by locating the server-side comment handling and the comment table schema, then verify the required foreign-key relationship. Implement storage for the comment content, author, and creation date, and confirm that both success and failure produce responses. Done means the database insertion and response behavior are covered for the comment feature.

Written by the indexing model from the issue text.