curl --request POST \
  --url https://marketplace-as-a-service.herokuapp.com/index.php/api/oauth2 \
  --header 'Content-Type: application/json' \
  --data '
{
  "username": "demo_user",
  "password": "demo_pass",
  "grant_type": "password"
}
'

import requests

url = "https://marketplace-as-a-service.herokuapp.com/index.php/api/oauth2"

payload = {
    "username": "demo_user",
    "password": "demo_pass",
    "grant_type": "password"
}
headers = {"Content-Type": "application/json"}

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

print(response.text)

const options = {
  method: 'POST',
  headers: {'Content-Type': 'application/json'},
  body: JSON.stringify({username: 'demo_user', password: 'demo_pass', grant_type: 'password'})
};

fetch('https://marketplace-as-a-service.herokuapp.com/index.php/api/oauth2', 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://marketplace-as-a-service.herokuapp.com/index.php/api/oauth2",
  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([
    'username' => 'demo_user',
    'password' => 'demo_pass',
    'grant_type' => 'password'
  ]),
  CURLOPT_HTTPHEADER => [
    "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://marketplace-as-a-service.herokuapp.com/index.php/api/oauth2"

	payload := strings.NewReader("{\n  \"username\": \"demo_user\",\n  \"password\": \"demo_pass\",\n  \"grant_type\": \"password\"\n}")

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

	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://marketplace-as-a-service.herokuapp.com/index.php/api/oauth2")
  .header("Content-Type", "application/json")
  .body("{\n  \"username\": \"demo_user\",\n  \"password\": \"demo_pass\",\n  \"grant_type\": \"password\"\n}")
  .asString();

require 'uri'
require 'net/http'

url = URI("https://marketplace-as-a-service.herokuapp.com/index.php/api/oauth2")

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

request = Net::HTTP::Post.new(url)
request["Content-Type"] = 'application/json'
request.body = "{\n  \"username\": \"demo_user\",\n  \"password\": \"demo_pass\",\n  \"grant_type\": \"password\"\n}"

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

{
  "access_token": "93019854-6B88-4997-9179-C1C50E7D2E9D",
  "expires_in": 3600,
  "refresh_token": "2495C12E-AFFA-40AD-8B91-61D7CEE3D5DC",
  "refresh_expires_in": 18000,
  "fuse_client_id_seq": null
}