Get competition info

{
    "contest": {
        "contest_id": 1,
        "title": "第一次练习",
        "subtitle": "22计算机3班",
        "difficulty": "简单",
        "password": "123456",
        "have_password": true,
        "is_visible": true,
        "start_at": "2024-08-19T00:00:00+08:00",
        "end_at": "2024-09-19T00:00:00+08:00"
    }
}