curl --request PUT \
  --url https://api.steppay.kr/api/v1/customers/{id} \
  --header 'Content-Type: application/json' \
  --header 'Secret-Token: <api-key>' \
  --data '
{
  "name": "고객 수정",
  "email": "test_modify@gmail.com",
  "phone": "010-1234-1234"
}
'

{
  "id": 1,
  "username": "test@gmail.com",
  "name": "고객 수정",
  "email": "test_modify@gmail.com",
  "phone": "01012341234",
  "code": null,
  "marketingSms": null,
  "marketingEmail": null,
  "marketingKakao": null,
  "createdAt": "9999-01-01T00:00:00"
}