curl -X POST \
  https://api.sakari.io/oauth2/token \
  -H 'Content-Type: application/json' \
  -d '{
  "grant_type": "client_credentials",
  "client_id": "12345678-1234-1234-1234-123456789012",
  "client_secret": "87654321-4321-4321-4321-098765432121"
}'

var settings = {
  "async": true,
  "crossDomain": true,
  "url": "https://api.sakari.io/oauth2/token",
  "method": "POST",
  "headers": {
    "Content-Type": "application/json"
  },
  "processData": false,
  "data": "{\n\t\"grant_type\": \"client_credentials\",\n\t\"client_id\": \"12345678-1234-1234-1234-123456789012\",\n\t\"client_secret\": \"87654321-4321-4321-4321-098765432121\"\n}"
}

$.ajax(settings).done(function (response) {
  console.log(response);
});

<?php

  $request = new HttpRequest();
  $request->setUrl('https://api.sakari.io/oauth2/token');
  $request->setMethod(HTTP_METH_POST);
  
  $request->setHeaders(array(
    'Content-Type' => 'application/json'
  ));
  
  $request->setBody('{
    "grant_type": "client_credentials",
    "client_id": "12345678-1234-1234-123456789012",
    "client_secret": "87654321-4321-4321-898765432121"
  }');
  
  try {
    $response = $request->send();
  
    echo $response->getBody();
  } catch (HttpException $ex) {
    echo $ex;
  }

import requests

url = "https://api.sakari.io/oauth2/token"

payload = {
    "grant_type": "client_credentials",
    "client_id": "00000000-0000-0000-0000-00000000000",
    "client_secret": "00000000-0000-0000-0000-00000000000"
}
headers = {"Content-Type": "application/json"}

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

print(response.text)

package main

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

func main() {

	url := "https://api.sakari.io/oauth2/token"

	payload := strings.NewReader("{\n  \"grant_type\": \"client_credentials\",\n  \"client_id\": \"00000000-0000-0000-0000-00000000000\",\n  \"client_secret\": \"00000000-0000-0000-0000-00000000000\"\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://api.sakari.io/oauth2/token")
  .header("Content-Type", "application/json")
  .body("{\n  \"grant_type\": \"client_credentials\",\n  \"client_id\": \"00000000-0000-0000-0000-00000000000\",\n  \"client_secret\": \"00000000-0000-0000-0000-00000000000\"\n}")
  .asString();

require 'uri'
require 'net/http'

url = URI("https://api.sakari.io/oauth2/token")

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  \"grant_type\": \"client_credentials\",\n  \"client_id\": \"00000000-0000-0000-0000-00000000000\",\n  \"client_secret\": \"00000000-0000-0000-0000-00000000000\"\n}"

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

{
  "access_token": "<string>",
  "token_type": "<string>"
}

{
  "success": true,
  "error": {
    "code": "CONT-010",
    "description": "Contact has requested no further communication"
  }
}

{
  "success": true,
  "error": {
    "code": "CONT-010",
    "description": "Contact has requested no further communication"
  }
}