curl --request GET \
  --url https://openapi.pluuug.com/v1/client/{client_id}

{
  "id": 123,
  "status": {
    "id": 123,
    "title": "<string>"
  },
  "companyName": "<string>",
  "inCharge": "<string>",
  "position": "<string>",
  "contact": "<string>",
  "email": "jsmith@example.com",
  "content": "<string>",
  "businessRegistrationNumber": "<string>",
  "ceoName": "<string>",
  "companyAddress": "<string>",
  "companyDetailAddress": "<string>",
  "businessType": "<string>",
  "businessClass": "<string>",
  "branchNumber": "<string>",
  "taxInvoiceEmail": "<string>",
  "fieldSet": [
    {
      "field": {
        "id": 123,
        "name": "<string>",
        "dataType": "S",
        "optionSet": [
          {
            "id": "<string>",
            "title": "<string>"
          }
        ],
        "memberSet": [
          {
            "id": 123,
            "nickname": "<string>",
            "email": "<string>",
            "isActive": true,
            "grade": {
              "id": 123,
              "title": "<string>"
            }
          }
        ]
      },
      "value": "<string>"
    }
  ]
}