curl --request POST \
  --url https://api.maesn.dev/accounting/customers \
  --header 'Content-Type: application/json' \
  --header 'X-ACCOUNT-KEY: <x-account-key>' \
  --header 'X-API-KEY: <x-api-key>' \
  --data '
{
  "addresses": [
    {
      "addressLine1": "Lucky street 1",
      "addressLine2": "2nd floor",
      "city": "Berlin",
      "countryCode": "DE",
      "postalCode": "10243",
      "type": "BILLING"
    }
  ],
  "companyName": "maesn",
  "contactType": "CONTACT_PERSON",
  "contactPersons": [
    {
      "emailAddresses": [
        {
          "email": "john.doe@company.com",
          "type": "BUSINESS"
        }
      ],
      "firstName": "John",
      "lastName": "Doe",
      "phoneNumbers": [
        {
          "number": "+49 7163307056",
          "type": "MOBILE"
        }
      ],
      "salutation": "Mr"
    }
  ],
  "documentId": "Z1248601M",
  "emailAddresses": [
    {
      "email": "john.doe@company.com",
      "type": "BUSINESS"
    }
  ],
  "number": "1042",
  "phoneNumbers": [
    {
      "number": "+49 7163307056",
      "type": "MOBILE"
    }
  ],
  "projectId": "3",
  "vatId": "DE123456789"
}
'

import requests

url = "https://api.maesn.dev/accounting/customers"

payload = {
    "addresses": [
        {
            "addressLine1": "Lucky street 1",
            "addressLine2": "2nd floor",
            "city": "Berlin",
            "countryCode": "DE",
            "postalCode": "10243",
            "type": "BILLING"
        }
    ],
    "companyName": "maesn",
    "contactType": "CONTACT_PERSON",
    "contactPersons": [
        {
            "emailAddresses": [
                {
                    "email": "john.doe@company.com",
                    "type": "BUSINESS"
                }
            ],
            "firstName": "John",
            "lastName": "Doe",
            "phoneNumbers": [
                {
                    "number": "+49 7163307056",
                    "type": "MOBILE"
                }
            ],
            "salutation": "Mr"
        }
    ],
    "documentId": "Z1248601M",
    "emailAddresses": [
        {
            "email": "john.doe@company.com",
            "type": "BUSINESS"
        }
    ],
    "number": "1042",
    "phoneNumbers": [
        {
            "number": "+49 7163307056",
            "type": "MOBILE"
        }
    ],
    "projectId": "3",
    "vatId": "DE123456789"
}
headers = {
    "X-API-KEY": "<x-api-key>",
    "X-ACCOUNT-KEY": "<x-account-key>",
    "Content-Type": "application/json"
}

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

print(response.text)

const options = {
  method: 'POST',
  headers: {
    'X-API-KEY': '<x-api-key>',
    'X-ACCOUNT-KEY': '<x-account-key>',
    'Content-Type': 'application/json'
  },
  body: JSON.stringify({
    addresses: [
      {
        addressLine1: 'Lucky street 1',
        addressLine2: '2nd floor',
        city: 'Berlin',
        countryCode: 'DE',
        postalCode: '10243',
        type: 'BILLING'
      }
    ],
    companyName: 'maesn',
    contactType: 'CONTACT_PERSON',
    contactPersons: [
      {
        emailAddresses: [{email: 'john.doe@company.com', type: 'BUSINESS'}],
        firstName: 'John',
        lastName: 'Doe',
        phoneNumbers: [{number: '+49 7163307056', type: 'MOBILE'}],
        salutation: 'Mr'
      }
    ],
    documentId: 'Z1248601M',
    emailAddresses: [{email: 'john.doe@company.com', type: 'BUSINESS'}],
    number: '1042',
    phoneNumbers: [{number: '+49 7163307056', type: 'MOBILE'}],
    projectId: '3',
    vatId: 'DE123456789'
  })
};

fetch('https://api.maesn.dev/accounting/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.maesn.dev/accounting/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([
    'addresses' => [
        [
                'addressLine1' => 'Lucky street 1',
                'addressLine2' => '2nd floor',
                'city' => 'Berlin',
                'countryCode' => 'DE',
                'postalCode' => '10243',
                'type' => 'BILLING'
        ]
    ],
    'companyName' => 'maesn',
    'contactType' => 'CONTACT_PERSON',
    'contactPersons' => [
        [
                'emailAddresses' => [
                                [
                                                                'email' => 'john.doe@company.com',
                                                                'type' => 'BUSINESS'
                                ]
                ],
                'firstName' => 'John',
                'lastName' => 'Doe',
                'phoneNumbers' => [
                                [
                                                                'number' => '+49 7163307056',
                                                                'type' => 'MOBILE'
                                ]
                ],
                'salutation' => 'Mr'
        ]
    ],
    'documentId' => 'Z1248601M',
    'emailAddresses' => [
        [
                'email' => 'john.doe@company.com',
                'type' => 'BUSINESS'
        ]
    ],
    'number' => '1042',
    'phoneNumbers' => [
        [
                'number' => '+49 7163307056',
                'type' => 'MOBILE'
        ]
    ],
    'projectId' => '3',
    'vatId' => 'DE123456789'
  ]),
  CURLOPT_HTTPHEADER => [
    "Content-Type: application/json",
    "X-ACCOUNT-KEY: <x-account-key>",
    "X-API-KEY: <x-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.maesn.dev/accounting/customers"

	payload := strings.NewReader("{\n  \"addresses\": [\n    {\n      \"addressLine1\": \"Lucky street 1\",\n      \"addressLine2\": \"2nd floor\",\n      \"city\": \"Berlin\",\n      \"countryCode\": \"DE\",\n      \"postalCode\": \"10243\",\n      \"type\": \"BILLING\"\n    }\n  ],\n  \"companyName\": \"maesn\",\n  \"contactType\": \"CONTACT_PERSON\",\n  \"contactPersons\": [\n    {\n      \"emailAddresses\": [\n        {\n          \"email\": \"john.doe@company.com\",\n          \"type\": \"BUSINESS\"\n        }\n      ],\n      \"firstName\": \"John\",\n      \"lastName\": \"Doe\",\n      \"phoneNumbers\": [\n        {\n          \"number\": \"+49 7163307056\",\n          \"type\": \"MOBILE\"\n        }\n      ],\n      \"salutation\": \"Mr\"\n    }\n  ],\n  \"documentId\": \"Z1248601M\",\n  \"emailAddresses\": [\n    {\n      \"email\": \"john.doe@company.com\",\n      \"type\": \"BUSINESS\"\n    }\n  ],\n  \"number\": \"1042\",\n  \"phoneNumbers\": [\n    {\n      \"number\": \"+49 7163307056\",\n      \"type\": \"MOBILE\"\n    }\n  ],\n  \"projectId\": \"3\",\n  \"vatId\": \"DE123456789\"\n}")

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

	req.Header.Add("X-API-KEY", "<x-api-key>")
	req.Header.Add("X-ACCOUNT-KEY", "<x-account-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.maesn.dev/accounting/customers")
  .header("X-API-KEY", "<x-api-key>")
  .header("X-ACCOUNT-KEY", "<x-account-key>")
  .header("Content-Type", "application/json")
  .body("{\n  \"addresses\": [\n    {\n      \"addressLine1\": \"Lucky street 1\",\n      \"addressLine2\": \"2nd floor\",\n      \"city\": \"Berlin\",\n      \"countryCode\": \"DE\",\n      \"postalCode\": \"10243\",\n      \"type\": \"BILLING\"\n    }\n  ],\n  \"companyName\": \"maesn\",\n  \"contactType\": \"CONTACT_PERSON\",\n  \"contactPersons\": [\n    {\n      \"emailAddresses\": [\n        {\n          \"email\": \"john.doe@company.com\",\n          \"type\": \"BUSINESS\"\n        }\n      ],\n      \"firstName\": \"John\",\n      \"lastName\": \"Doe\",\n      \"phoneNumbers\": [\n        {\n          \"number\": \"+49 7163307056\",\n          \"type\": \"MOBILE\"\n        }\n      ],\n      \"salutation\": \"Mr\"\n    }\n  ],\n  \"documentId\": \"Z1248601M\",\n  \"emailAddresses\": [\n    {\n      \"email\": \"john.doe@company.com\",\n      \"type\": \"BUSINESS\"\n    }\n  ],\n  \"number\": \"1042\",\n  \"phoneNumbers\": [\n    {\n      \"number\": \"+49 7163307056\",\n      \"type\": \"MOBILE\"\n    }\n  ],\n  \"projectId\": \"3\",\n  \"vatId\": \"DE123456789\"\n}")
  .asString();

require 'uri'
require 'net/http'

url = URI("https://api.maesn.dev/accounting/customers")

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

request = Net::HTTP::Post.new(url)
request["X-API-KEY"] = '<x-api-key>'
request["X-ACCOUNT-KEY"] = '<x-account-key>'
request["Content-Type"] = 'application/json'
request.body = "{\n  \"addresses\": [\n    {\n      \"addressLine1\": \"Lucky street 1\",\n      \"addressLine2\": \"2nd floor\",\n      \"city\": \"Berlin\",\n      \"countryCode\": \"DE\",\n      \"postalCode\": \"10243\",\n      \"type\": \"BILLING\"\n    }\n  ],\n  \"companyName\": \"maesn\",\n  \"contactType\": \"CONTACT_PERSON\",\n  \"contactPersons\": [\n    {\n      \"emailAddresses\": [\n        {\n          \"email\": \"john.doe@company.com\",\n          \"type\": \"BUSINESS\"\n        }\n      ],\n      \"firstName\": \"John\",\n      \"lastName\": \"Doe\",\n      \"phoneNumbers\": [\n        {\n          \"number\": \"+49 7163307056\",\n          \"type\": \"MOBILE\"\n        }\n      ],\n      \"salutation\": \"Mr\"\n    }\n  ],\n  \"documentId\": \"Z1248601M\",\n  \"emailAddresses\": [\n    {\n      \"email\": \"john.doe@company.com\",\n      \"type\": \"BUSINESS\"\n    }\n  ],\n  \"number\": \"1042\",\n  \"phoneNumbers\": [\n    {\n      \"number\": \"+49 7163307056\",\n      \"type\": \"MOBILE\"\n    }\n  ],\n  \"projectId\": \"3\",\n  \"vatId\": \"DE123456789\"\n}"

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

{
  "meta": {
    "warnings": [
      "Field not used by target system"
    ],
    "pagination": {
      "total": 125,
      "perPage": 50,
      "currentPage": 1,
      "totalPages": 3
    }
  },
  "data": {
    "id": "92c4f3a2-5b8e-4d1b-8a0c-9f6e7d2f3e4b",
    "addresses": [
      {
        "addressLine1": "Lucky street 1",
        "addressLine2": "2nd floor",
        "city": "Berlin",
        "countryCode": "DE",
        "postalCode": "10243",
        "type": "BILLING"
      }
    ],
    "companyName": "maesn",
    "contactType": "CONTACT_PERSON",
    "contactPersons": [
      {
        "emailAddresses": [
          {
            "email": "john.doe@company.com",
            "type": "BUSINESS"
          }
        ],
        "firstName": "John",
        "lastName": "Doe",
        "phoneNumbers": [
          {
            "number": "+49 7163307056",
            "type": "MOBILE"
          }
        ],
        "salutation": "Mr"
      }
    ],
    "documentId": "Z1248601M",
    "emailAddresses": [
      {
        "email": "john.doe@company.com",
        "type": "BUSINESS"
      }
    ],
    "number": "1042",
    "phoneNumbers": [
      {
        "number": "+49 7163307056",
        "type": "MOBILE"
      }
    ],
    "projectId": "3",
    "updatedDate": "2018-01-01T13:00:00.000Z",
    "vatId": "DE123456789"
  }
}