curl --request POST \
  --url https://api.grainfinance.co/v1/customers \
  --header 'Authorization: Basic <encoded-value>' \
  --header 'Content-Type: application/json' \
  --data @- <<EOF
{
  "companyName": "Ollivander's Wand Shop",
  "companyCountry": "GB",
  "externalCustomerId": "630231b3ae0d7e9e5097ad35",
  "contactEmail": "customer@company.com",
  "contactFullName": "Garrick Ollivander",
  "contactPhoneNumber": "+12125551234",
  "companyAddress": "12 Diagon Alley",
  "companyCity": "London",
  "companyState": "London",
  "companyTaxId": "123-45-6789",
  "extraFields": {
    "field_a": "value_a",
    "field_b": "value_b"
  }
}
EOF

import requests

url = "https://api.grainfinance.co/v1/customers"

payload = {
    "companyName": "Ollivander's Wand Shop",
    "companyCountry": "GB",
    "externalCustomerId": "630231b3ae0d7e9e5097ad35",
    "contactEmail": "customer@company.com",
    "contactFullName": "Garrick Ollivander",
    "contactPhoneNumber": "+12125551234",
    "companyAddress": "12 Diagon Alley",
    "companyCity": "London",
    "companyState": "London",
    "companyTaxId": "123-45-6789",
    "extraFields": {
        "field_a": "value_a",
        "field_b": "value_b"
    }
}
headers = {
    "Authorization": "Basic <encoded-value>",
    "Content-Type": "application/json"
}

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

print(response.text)

const options = {
  method: 'POST',
  headers: {Authorization: 'Basic <encoded-value>', 'Content-Type': 'application/json'},
  body: JSON.stringify({
    companyName: 'Ollivander\'s Wand Shop',
    companyCountry: 'GB',
    externalCustomerId: '630231b3ae0d7e9e5097ad35',
    contactEmail: 'customer@company.com',
    contactFullName: 'Garrick Ollivander',
    contactPhoneNumber: '+12125551234',
    companyAddress: '12 Diagon Alley',
    companyCity: 'London',
    companyState: 'London',
    companyTaxId: '123-45-6789',
    extraFields: {field_a: 'value_a', field_b: 'value_b'}
  })
};

fetch('https://api.grainfinance.co/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.grainfinance.co/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([
    'companyName' => 'Ollivander\'s Wand Shop',
    'companyCountry' => 'GB',
    'externalCustomerId' => '630231b3ae0d7e9e5097ad35',
    'contactEmail' => 'customer@company.com',
    'contactFullName' => 'Garrick Ollivander',
    'contactPhoneNumber' => '+12125551234',
    'companyAddress' => '12 Diagon Alley',
    'companyCity' => 'London',
    'companyState' => 'London',
    'companyTaxId' => '123-45-6789',
    'extraFields' => [
        'field_a' => 'value_a',
        'field_b' => 'value_b'
    ]
  ]),
  CURLOPT_HTTPHEADER => [
    "Authorization: Basic <encoded-value>",
    "Content-Type: application/json"
  ],
]);

$response = curl_exec($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.grainfinance.co/v1/customers"

	payload := strings.NewReader("{\n  \"companyName\": \"Ollivander's Wand Shop\",\n  \"companyCountry\": \"GB\",\n  \"externalCustomerId\": \"630231b3ae0d7e9e5097ad35\",\n  \"contactEmail\": \"customer@company.com\",\n  \"contactFullName\": \"Garrick Ollivander\",\n  \"contactPhoneNumber\": \"+12125551234\",\n  \"companyAddress\": \"12 Diagon Alley\",\n  \"companyCity\": \"London\",\n  \"companyState\": \"London\",\n  \"companyTaxId\": \"123-45-6789\",\n  \"extraFields\": {\n    \"field_a\": \"value_a\",\n    \"field_b\": \"value_b\"\n  }\n}")

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

	req.Header.Add("Authorization", "Basic <encoded-value>")
	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.grainfinance.co/v1/customers")
  .header("Authorization", "Basic <encoded-value>")
  .header("Content-Type", "application/json")
  .body("{\n  \"companyName\": \"Ollivander's Wand Shop\",\n  \"companyCountry\": \"GB\",\n  \"externalCustomerId\": \"630231b3ae0d7e9e5097ad35\",\n  \"contactEmail\": \"customer@company.com\",\n  \"contactFullName\": \"Garrick Ollivander\",\n  \"contactPhoneNumber\": \"+12125551234\",\n  \"companyAddress\": \"12 Diagon Alley\",\n  \"companyCity\": \"London\",\n  \"companyState\": \"London\",\n  \"companyTaxId\": \"123-45-6789\",\n  \"extraFields\": {\n    \"field_a\": \"value_a\",\n    \"field_b\": \"value_b\"\n  }\n}")
  .asString();

require 'uri'
require 'net/http'

url = URI("https://api.grainfinance.co/v1/customers")

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

request = Net::HTTP::Post.new(url)
request["Authorization"] = 'Basic <encoded-value>'
request["Content-Type"] = 'application/json'
request.body = "{\n  \"companyName\": \"Ollivander's Wand Shop\",\n  \"companyCountry\": \"GB\",\n  \"externalCustomerId\": \"630231b3ae0d7e9e5097ad35\",\n  \"contactEmail\": \"customer@company.com\",\n  \"contactFullName\": \"Garrick Ollivander\",\n  \"contactPhoneNumber\": \"+12125551234\",\n  \"companyAddress\": \"12 Diagon Alley\",\n  \"companyCity\": \"London\",\n  \"companyState\": \"London\",\n  \"companyTaxId\": \"123-45-6789\",\n  \"extraFields\": {\n    \"field_a\": \"value_a\",\n    \"field_b\": \"value_b\"\n  }\n}"

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

{
  "id": "1b0ada1e-fa1b-4cfe-a553-01b340c5650e"
}

{
  "id": "1b0ada1e-fa1b-4cfe-a553-01b340c5650e"
}

{
  "message": "Can't perform this action",
  "reason": "Supplied object is in *Cancelled* state, which prevents performing this action"
}

{
  "message": "Can't perform this action",
  "reason": "Supplied object is in *Cancelled* state, which prevents performing this action"
}