curl --request POST \
  --url https://api.steppay.kr/api/v1/customers \
  --header 'Content-Type: application/json' \
  --header 'Secret-Token: <api-key>' \
  --data '
{
  "name": "테스트 고객",
  "username": "test@gmail.com",
  "email": "test@gmail.com",
  "phone": "010-1234-5678"
}
'

import requests

url = "https://api.steppay.kr/api/v1/customers"

payload = {
    "name": "테스트 고객",
    "username": "test@gmail.com",
    "email": "test@gmail.com",
    "phone": "010-1234-5678"
}
headers = {
    "Secret-Token": "<api-key>",
    "Content-Type": "application/json"
}

response = requests.post(url, json=payload, headers=headers)

print(response.text)

const options = {
  method: 'POST',
  headers: {'Secret-Token': '<api-key>', 'Content-Type': 'application/json'},
  body: JSON.stringify({
    name: '테스트 고객',
    username: 'test@gmail.com',
    email: 'test@gmail.com',
    phone: '010-1234-5678'
  })
};

fetch('https://api.steppay.kr/api/v1/customers', options)
  .then(res => res.json())
  .then(res => console.log(res))
  .catch(err => console.error(err));

<?php

$curl = curl_init();

curl_setopt_array($curl, [
  CURLOPT_URL => "https://api.steppay.kr/api/v1/customers",
  CURLOPT_RETURNTRANSFER => true,
  CURLOPT_ENCODING => "",
  CURLOPT_MAXREDIRS => 10,
  CURLOPT_TIMEOUT => 30,
  CURLOPT_HTTP_VERSION => CURL_HTTP_VERSION_1_1,
  CURLOPT_CUSTOMREQUEST => "POST",
  CURLOPT_POSTFIELDS => json_encode([
    'name' => '테스트 고객',
    'username' => 'test@gmail.com',
    'email' => 'test@gmail.com',
    'phone' => '010-1234-5678'
  ]),
  CURLOPT_HTTPHEADER => [
    "Content-Type: application/json",
    "Secret-Token: <api-key>"
  ],
]);

$response = curl_exec($curl);
$err = curl_error($curl);

curl_close($curl);

if ($err) {
  echo "cURL Error #:" . $err;
} else {
  echo $response;
}

package main

import (
	"fmt"
	"strings"
	"net/http"
	"io"
)

func main() {

	url := "https://api.steppay.kr/api/v1/customers"

	payload := strings.NewReader("{\n  \"name\": \"테스트 고객\",\n  \"username\": \"test@gmail.com\",\n  \"email\": \"test@gmail.com\",\n  \"phone\": \"010-1234-5678\"\n}")

	req, _ := http.NewRequest("POST", url, payload)

	req.Header.Add("Secret-Token", "<api-key>")
	req.Header.Add("Content-Type", "application/json")

	res, _ := http.DefaultClient.Do(req)

	defer res.Body.Close()
	body, _ := io.ReadAll(res.Body)

	fmt.Println(string(body))

}

HttpResponse<String> response = Unirest.post("https://api.steppay.kr/api/v1/customers")
  .header("Secret-Token", "<api-key>")
  .header("Content-Type", "application/json")
  .body("{\n  \"name\": \"테스트 고객\",\n  \"username\": \"test@gmail.com\",\n  \"email\": \"test@gmail.com\",\n  \"phone\": \"010-1234-5678\"\n}")
  .asString();

require 'uri'
require 'net/http'

url = URI("https://api.steppay.kr/api/v1/customers")

http = Net::HTTP.new(url.host, url.port)
http.use_ssl = true

request = Net::HTTP::Post.new(url)
request["Secret-Token"] = '<api-key>'
request["Content-Type"] = 'application/json'
request.body = "{\n  \"name\": \"테스트 고객\",\n  \"username\": \"test@gmail.com\",\n  \"email\": \"test@gmail.com\",\n  \"phone\": \"010-1234-5678\"\n}"

response = http.request(request)
puts response.read_body

{
  "id": 1,
  "username": "test@gmail.com",
  "name": "테스트 고객",
  "email": "test@gmail.com",
  "phone": "01012345678",
  "code": "customer_AbCdEfGhI",
  "marketingSms": false,
  "marketingEmail": false,
  "marketingKakao": false,
  "createdAt": "9999-01-01T00:00:00.000000"
}

{
  "errorCode": "<string>",
  "traceId": "<string>",
  "errorMessage": "<string>",
  "details": {}
}