Oauth for Untappd not working
Hi all! I'm using Strapi for a personal BeerApp project, and I'm trying to get Oauth2 for Untappd working. At the moment however, I don't seem to send the correct values to Untappd, as I'm getting indications that I'm not sending the required params in the URL. 

I have the following Grant configuration:
```
    untappd: {
      authorize_url: "https://untappd.com/oauth/authenticate",
      access_url: "https://untappd.com/oauth/authorize",
      oauth: 2,
      key: "",
      secret: "",
      callback: `${strapi.config.server.url}/auth/untappd/callback`,
```

I am getting back the 'code' parameter to the callback URL, but after that it doesn't work. Untappd requires a GET request to get the access_token back with the following parameters:

```
https://untappd.com/oauth/authorize/?client_id=CLIENTID&client_secret=CLIENTSECRET&response_type=code&redirect_url=REDIRECT_URL&code=CODE
```
However, I get the message from Untappd:
```
http_code = 500. Param_error: Missing either the client_id, redirect_url, client_secret or code parameter. Please check your request and try again
```
I already tried to use the `token_endpoint_auth_method: "client_secret_basic"`, as to my understanding Grant is using a POST request to get the access_token, right? But adding this option to the config this doesn't change anything. 

Does anyone have a clue what to do? 