Microsoft GraphQL - has been blocked by CORS policy: Response to preflight request doesn't pass access control check: No 'Access-Control-Allow-Origin : I'm running my Vue app locally from http://localhost:8080 and I keep getting a slew of CORS errors, I've added the Access-Control-Allow-Origin header as seen blow but keep getting the following warning:

' from origin 'http://localhost:8080' has been blocked by CORS policy: Response to preflight request doesn't pass access control check: No 'Access-Control-Allow-Origin' header is present on the requested resource. If an opaque response serves your needs, set the request's mode to 'no-cors' to fetch the resource with CORS disabled.

```
const graphCall = () => {

  let tokenOptions = {
    method: 'POST',
    uri: 'https://login.microsoftonline.com/**key**/oauth2/v2.0/token',
    headers: {
      'Access-Control-Allow-Origin': 'http://localhost:8080',
      'contentType': 'application/x-www-form-urlencoded'
    },

    form: {
      grant_type: VUE_APP_GRANT_TYPE,
      client_secret: VUE_APP_CLIENT_SECRET,
      scope: VUE_APP_SCOPE,
      client_id: VUE_APP_CLIENT_ID
    }

  };

  return rp(tokenOptions)
    .then(data => {

      console.log(data)


    }).catch((err) => {

      console.log(err);

    });
};

```

I've tried adding mode: 'no-cors' but just get the following - Error: Invalid value for opts.mode

I've also tried '*' as the access control origin but to no avail.

Is there a way through this CORS nightmare as we need to make this call to retrieve a key! Pretty new to all of this so please bare with me if I've not been as descriptive as I could have been!