curl --request POST \
  --url https://api.mijnklantportaal.nl/v1/customer-invoices \
  --header 'Authorization: Bearer <token>' \
  --header 'Content-Type: multipart/form-data' \
  --form customerId=cst_abc12345def678 \
  --form invoiceNumber=2014-001 \
  --form issuedAt=2024-04-31 \
  --form amount=12.95 \
  --form pdf='@example-file' \
  --form dueAt=2024-05-28 \
  --form 'paidAt=2024-05-11 12:59:00' \
  --form sendNotification=true

import requests

url = "https://api.mijnklantportaal.nl/v1/customer-invoices"

files = { "pdf": ("example-file", open("example-file", "rb")) }
payload = {
    "customerId": "cst_abc12345def678",
    "invoiceNumber": "2014-001",
    "issuedAt": "2024-04-31",
    "amount": "12.95",
    "dueAt": "2024-05-28",
    "paidAt": "2024-05-11 12:59:00",
    "sendNotification": "true"
}
headers = {"Authorization": "Bearer <token>"}

response = requests.post(url, data=payload, files=files, headers=headers)

print(response.text)

const form = new FormData();
form.append('customerId', 'cst_abc12345def678');
form.append('invoiceNumber', '2014-001');
form.append('issuedAt', '2024-04-31');
form.append('amount', '12.95');
form.append('pdf', '<string>');
form.append('dueAt', '2024-05-28');
form.append('paidAt', '2024-05-11 12:59:00');
form.append('sendNotification', 'true');

const options = {method: 'POST', headers: {Authorization: 'Bearer <token>'}};

options.body = form;

fetch('https://api.mijnklantportaal.nl/v1/customer-invoices', 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.mijnklantportaal.nl/v1/customer-invoices",
  CURLOPT_RETURNTRANSFER => true,
  CURLOPT_ENCODING => "",
  CURLOPT_MAXREDIRS => 10,
  CURLOPT_TIMEOUT => 30,
  CURLOPT_HTTP_VERSION => CURL_HTTP_VERSION_1_1,
  CURLOPT_CUSTOMREQUEST => "POST",
  CURLOPT_POSTFIELDS => "-----011000010111000001101001\r\nContent-Disposition: form-data; name=\"customerId\"\r\n\r\ncst_abc12345def678\r\n-----011000010111000001101001\r\nContent-Disposition: form-data; name=\"invoiceNumber\"\r\n\r\n2014-001\r\n-----011000010111000001101001\r\nContent-Disposition: form-data; name=\"issuedAt\"\r\n\r\n2024-04-31\r\n-----011000010111000001101001\r\nContent-Disposition: form-data; name=\"amount\"\r\n\r\n12.95\r\n-----011000010111000001101001\r\nContent-Disposition: form-data; name=\"pdf\"; filename=\"example-file\"\r\nContent-Type: application/octet-stream\r\n\r\n<string>\r\n-----011000010111000001101001\r\nContent-Disposition: form-data; name=\"dueAt\"\r\n\r\n2024-05-28\r\n-----011000010111000001101001\r\nContent-Disposition: form-data; name=\"paidAt\"\r\n\r\n2024-05-11 12:59:00\r\n-----011000010111000001101001\r\nContent-Disposition: form-data; name=\"sendNotification\"\r\n\r\ntrue\r\n-----011000010111000001101001--",
  CURLOPT_HTTPHEADER => [
    "Authorization: Bearer <token>",
    "Content-Type: multipart/form-data"
  ],
]);

$response = curl_exec($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.mijnklantportaal.nl/v1/customer-invoices"

	payload := strings.NewReader("-----011000010111000001101001\r\nContent-Disposition: form-data; name=\"customerId\"\r\n\r\ncst_abc12345def678\r\n-----011000010111000001101001\r\nContent-Disposition: form-data; name=\"invoiceNumber\"\r\n\r\n2014-001\r\n-----011000010111000001101001\r\nContent-Disposition: form-data; name=\"issuedAt\"\r\n\r\n2024-04-31\r\n-----011000010111000001101001\r\nContent-Disposition: form-data; name=\"amount\"\r\n\r\n12.95\r\n-----011000010111000001101001\r\nContent-Disposition: form-data; name=\"pdf\"; filename=\"example-file\"\r\nContent-Type: application/octet-stream\r\n\r\n<string>\r\n-----011000010111000001101001\r\nContent-Disposition: form-data; name=\"dueAt\"\r\n\r\n2024-05-28\r\n-----011000010111000001101001\r\nContent-Disposition: form-data; name=\"paidAt\"\r\n\r\n2024-05-11 12:59:00\r\n-----011000010111000001101001\r\nContent-Disposition: form-data; name=\"sendNotification\"\r\n\r\ntrue\r\n-----011000010111000001101001--")

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

	req.Header.Add("Authorization", "Bearer <token>")

	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.mijnklantportaal.nl/v1/customer-invoices")
  .header("Authorization", "Bearer <token>")
  .body("-----011000010111000001101001\r\nContent-Disposition: form-data; name=\"customerId\"\r\n\r\ncst_abc12345def678\r\n-----011000010111000001101001\r\nContent-Disposition: form-data; name=\"invoiceNumber\"\r\n\r\n2014-001\r\n-----011000010111000001101001\r\nContent-Disposition: form-data; name=\"issuedAt\"\r\n\r\n2024-04-31\r\n-----011000010111000001101001\r\nContent-Disposition: form-data; name=\"amount\"\r\n\r\n12.95\r\n-----011000010111000001101001\r\nContent-Disposition: form-data; name=\"pdf\"; filename=\"example-file\"\r\nContent-Type: application/octet-stream\r\n\r\n<string>\r\n-----011000010111000001101001\r\nContent-Disposition: form-data; name=\"dueAt\"\r\n\r\n2024-05-28\r\n-----011000010111000001101001\r\nContent-Disposition: form-data; name=\"paidAt\"\r\n\r\n2024-05-11 12:59:00\r\n-----011000010111000001101001\r\nContent-Disposition: form-data; name=\"sendNotification\"\r\n\r\ntrue\r\n-----011000010111000001101001--")
  .asString();

require 'uri'
require 'net/http'

url = URI("https://api.mijnklantportaal.nl/v1/customer-invoices")

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

request = Net::HTTP::Post.new(url)
request["Authorization"] = 'Bearer <token>'
request.body = "-----011000010111000001101001\r\nContent-Disposition: form-data; name=\"customerId\"\r\n\r\ncst_abc12345def678\r\n-----011000010111000001101001\r\nContent-Disposition: form-data; name=\"invoiceNumber\"\r\n\r\n2014-001\r\n-----011000010111000001101001\r\nContent-Disposition: form-data; name=\"issuedAt\"\r\n\r\n2024-04-31\r\n-----011000010111000001101001\r\nContent-Disposition: form-data; name=\"amount\"\r\n\r\n12.95\r\n-----011000010111000001101001\r\nContent-Disposition: form-data; name=\"pdf\"; filename=\"example-file\"\r\nContent-Type: application/octet-stream\r\n\r\n<string>\r\n-----011000010111000001101001\r\nContent-Disposition: form-data; name=\"dueAt\"\r\n\r\n2024-05-28\r\n-----011000010111000001101001\r\nContent-Disposition: form-data; name=\"paidAt\"\r\n\r\n2024-05-11 12:59:00\r\n-----011000010111000001101001\r\nContent-Disposition: form-data; name=\"sendNotification\"\r\n\r\ntrue\r\n-----011000010111000001101001--"

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

{
  "id": "inv_abc12345def678",
  "customerId": "cst_abc12345def678",
  "invoiceNumber": "2024-001",
  "issuedAt": "2024-04-29",
  "dueAt": "2024-05-28",
  "currency": "EUR",
  "amount": "12.95",
  "paidAt": "2024-05-28T21:00:00+02:00",
  "createdAt": "2024-04-29T21:00:00+02:00",
  "links": {
    "customer": {
      "href": "https://api.mijnklantportaal.nl/v1/customers/cst_abc12345def678",
      "type": "application/json"
    },
    "onlinePaymentLink": {
      "href": "https://portal.mijnklantportaal.nl/public-invoice/inv_abc123/pay/123-abc",
      "type": "text/html"
    }
  }
}

{
  "message": "<string>"
}

{
  "message": "<string>"
}