Help converting url rest authentication to powerquery with post.

I am trying to authenticate to a rest service.  I usually built a query in python with url encoder and have no troubles. 

The website documentation looke like this. 

$.post("/Services/General/Authentication/Authenticate",
    { data: JSON.stringify({ LoginName: "jdoe",Password: "jdoe" }) },
    function (data) {
        var token = JSON.parse(data);
    }
);

or it will take a url directly like so. 

http://localhost/Services/General/Authentication/Authenticate?data={"LoginName":"jdoe","Password":"jdoe"}

 In Python my code looks like this: 

def login():
    """ Login to site and return the token"""

    log.info("Connect to site and Get Security Settings")

    payload = {"LoginName":"login","Password":"pwd"}
                
    response = requests.get('https://localhost/services/General/Authentication/Authenticate?data=' + json.dumps(payload))
    jrespon = response.json()
    token = "&token=" + jrespon[u'Value'][u'Token']

    return token

Currently my query looks like this. 

let
    data = [    LoginName = "login",
                Password = "pwd"        
    ],

    header = [    #"Content-Type"= "application/json"],

    response = Web.Contents("https://localhost/Services/General/Authentication/Authenticate", [Content=Json.FromValue(data), Headers=header]),
    out = Json.Document(response)
    
in
    out

Any advice would be greatly appreciated.  I have tried multiple different ways, but I am always getting an invalid login name or invalid login name field error.  Fiddler seams to show that they are coming in as data and not being appended to the url.  I need to post not  get so if I just build the url as a string I can't get what I need either.  

Thanks in advance.