Add authorization header to Snapchat login callback using passport js strategy

I'm trying to integrate login using Snapchat to my application. In order to do that I need to add an authorization bearer to the callback request to my application so I can verify the client. According to Snapchat guide I need to use _qs or Axios to create the request:

// ******************** URL Builder Helper ***********************

var _qs = require("qs"); // Will need to 'npm install qs'

var getAuthCodeRedirectURL = function getAuthCodeRedirectURL(
  clientId,
  redirectUri,
  scopeList,
  state
) {
  var SNAP_ACCOUNTS_LOGIN_URL =
    "https://accounts.snapchat.com/accounts/oauth2/auth";
  var scope = scopeList.join(" ");
  var loginQS = {
    client_id: clientId,
    redirect_uri: redirectUri,
    response_type: "code",
    scope: scope,
    state: state,
  };

  var stringifyLoginQS = _qs.stringify(loginQS);
  return SNAP_ACCOUNTS_LOGIN_URL + "?" + stringifyLoginQS;
};

However I'm not sure how I can include the link in the passport.js strategy.

Can you clarify on how it works?

To pass the Authorization header, you have to set up the headers in the request library:

// Set headers
const headers = {
    Authorization: "Basic " + authorizationHeaderBase64,
};

// Configure access token POST request
const options = {
    url: SNAPCHAT_AUTH_ENDPOINT,
    method: "POST",
    headers: headers,
    form: {...},
};

request(options)

However, if you use the Passport authentication, just using the keys and setting up the config like in the docs should do the trick:

passport.use(new SnapchatStrategy({
    clientID: snapchat_APP_ID,
    clientSecret: snapchat_APP_SECRET,
    callbackURL: "http://localhost:3000/auth/snapchat/callback"
  },
  function(accessToken, refreshToken, profile, cb) {
    User.findOrCreate({ snapchatId: profile.id }, function (err, user) {
      return cb(err, user);
    });
  }
));

app.get('/auth/snapchat',
  passport.authenticate('snapchat'));

app.get('/auth/snapchat/callback',
  passport.authenticate('snapchat', { failureRedirect: '/login' }),
  function(req, res) {
    // Successful authorization, redirect home.
    res.redirect('/');
  });