Unable to do Oauth

Hello,
I was trying to do Oauth but got error {“error”:”invalid_client”,”error_description”:”The required \”client_id\” parameter is missing.”}.
I am giving the same client id which I got while registering on creating app on WordPress developer account.
I am hitting post request and here is my code

def redirect1(request):
    url = 'https://public-api.wordpress.com/oauth2/authorize?redirect_uri=https://127.0.0.1:8000/main/redirect' \
          '/&response_type=code&blog=1234&client_id=68733'
    return redirect(url)

def redirect(request):
    code = request.GET['code']

    url = 'https://public-api.wordpress.com/oauth2/token'
    payload = {
        "client_id": "68733",
        "redirect_uri": "https://127.0.0.1:8000/main/redirect/",
        "client_secret": "pasted which I got from my app",
        "code": code,
        "grant_type": "authorization_code",
    }
    header = {"Content-Type": "application/json"}
    response = requests.post(url=url, data=json.dumps(payload), headers=header)
    return JsonResponse(response.json())

I also tried following-
1. giving client_id as integer
2. header = {“Content-Type”: “application/x-www-form-urlencoded”}

I am following this link