curl --request POST \
  --url https://rest.yafacture.com/validadores/sat/xml \
  --header 'x-api-key: <api-key>'

const options = {method: 'POST', headers: {'x-api-key': '<api-key>'}};

fetch('https://rest.yafacture.com/validadores/sat/xml', options)
  .then(res => res.json())
  .then(res => console.log(res))
  .catch(err => console.error(err));

import requests

url = "https://rest.yafacture.com/validadores/sat/xml"

headers = {"x-api-key": "<api-key>"}

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

print(response.text)

<?php

$curl = curl_init();

curl_setopt_array($curl, [
  CURLOPT_URL => "https://rest.yafacture.com/validadores/sat/xml",
  CURLOPT_RETURNTRANSFER => true,
  CURLOPT_ENCODING => "",
  CURLOPT_MAXREDIRS => 10,
  CURLOPT_TIMEOUT => 30,
  CURLOPT_HTTP_VERSION => CURL_HTTP_VERSION_1_1,
  CURLOPT_CUSTOMREQUEST => "POST",
  CURLOPT_HTTPHEADER => [
    "x-api-key: <api-key>"
  ],
]);

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

curl_close($curl);

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

HttpResponse<String> response = Unirest.post("https://rest.yafacture.com/validadores/sat/xml")
  .header("x-api-key", "<api-key>")
  .asString();

package main

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

func main() {

	url := "https://rest.yafacture.com/validadores/sat/xml"

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

	req.Header.Add("x-api-key", "<api-key>")

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

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

	fmt.Println(string(body))

}

{
  "message": "Forbidden resource",
  "error": "Forbidden",
  "statusCode": 403
}