{
  "registrations": [
    {
      "id": "R0001",
      "activity_id": "A0001",
      "user_id": "U0001",
      "registration_time": "2024-04-15 14:30:00",
      "status": "confirmed",
      "custom_fields": [
        {
          "field_name": "experience_level",
          "field_type": "select",
          "field_label": "Vue.js经验水平",
          "field_options": ["入门", "进阶", "专家"]
        }
      ],
      "custom_answers": {
        "experience_level": "进阶"
      },
      "notes": "期待参加读书会！",
      "created_at": "2024-04-15 14:30:00",
      "updated_at": "2024-04-15 14:30:00"
    }
  ]
}