curl --request POST \
  --url https://api.steppay.kr/api/v1/cover/customer \
  --header 'Content-Type: application/json' \
  --header 'Secret-Token: <api-key>' \
  --data '
{
  "name": "<string>",
  "email": "<string>",
  "phone": "<string>",
  "replaceIfExists": true,
  "partnerCustomerId": "<string>"
}
'

{
  "id": 123,
  "name": "<string>",
  "email": "<string>",
  "phone": "<string>",
  "partnerCustomerId": "<string>"
}