그룹에 가입

METHOD	URL
POST	/group/join

Request.body

{
    "groupCode":"MzczNTg3"
}

Response

{
    "id": 1,
    "createdAt": "2021-11-04T02:52:53.590Z",
    "updatedAt": "2021-11-04T02:52:53.590Z",
    "name": "hello",
    "code": "MzczNTg3",
    "thumbnail": null
}