https://mongodb-documentation.readthedocs.io/en/latest/use-cases/storing-comments.html#gsc.tab=0
https://granora2019.tistory.com/entry/NodeJS%EC%99%80-MongoDB%EB%A1%9C-SNS-%EB%A7%8C%EB%93%A4%EC%96%B4%EB%B3%B4%EA%B8%B0-userment-%EB%8C%93%EA%B8%80%EB%8C%80%EB%8C%93%EA%B8%80-%EB%9D%BC%EC%9A%B0%ED%84%B0
https://stackoverflow.com/questions/51793672/mongodb-schema-like-a-comment-or-a-post
