M Language - How to get JSON in HTTP Request Body? (Vimeo API Unsupported Grant Type Error) - json

Question

I am attempting to create my first PowerBI Custom Connecter to connect to the Vimeo API. I am stuck on the final step of the authorization flow - getting back an access token. When trying out the Connecter in PowerBI, it seems to authenticate properly when I hit the access token endpoint, but I get back a warning "[unsupported_grant_type] Unsupported grant type"
It appears I am not sending the grant_type properly in the request. Here are Vimeo's requirements of what is sent along in the header and body of the request:
Header
Set value to
Authorization
basic base64_encode(x:y), where x is the client identifier and y is the client secret
Content-Type
application/json
Accept
application/vnd.vimeo.*+json;version=3.4
"In the request body, send the grant_type field with the value authorization_code. You must also set code to the authorization code string that you just received and redirect_uri to the redirect URI that you specified previously — don't use a different redirect URI."
{
"grant_type": "authorization_code",
"code": "{code}",
"redirect_uri": "{redirect_uri}"
}
Here is a snippet of code from the Customer Connector I am building. It is within this TokenMethod function that I am trying to fulfill the requirements of the table above. I am getting the sense I am not correctly placing the JSON in the body of the request, but I am stuck on what to try next:
TokenMethod = (grantType, tokenField, code) =>
let
queryString = [
grant_type = "authorization_code",
redirect_uri = redirect_uri,
client_id = client_id,
client_secret = client_secret
],
queryWithCode = Record.AddField(queryString, tokenField, code),
authKey = "Basic " & Binary.ToText(Text.ToBinary("client_id:client_secret"),BinaryEncoding.Base64),
tokenResponse = Web.Contents(token_uri, [
Content = Text.ToBinary(Uri.BuildQueryString(queryWithCode)),
Headers = [
#"Authorization" = authKey,
#"Content-type" = "application/json",
#"Accept" = "application/vnd.vimeo.*+json;version=3.4"
],
ManualStatusHandling = {400}
]),
body = Json.Document(tokenResponse),
result = if (Record.HasFields(body, {"error", "error_description"})) then
error Error.Record(body[error], body[error_description], body)
else
body
in
result;
I'm wondering if someone could please point out where I might be going astray in the code and why I am receiving the [unsupported_grant_type] error.
Many thanks for your time!

Answer 1

I changed Content-Type to "application/x-www-form-urlencoded" and it worked!