code: function (req, res, next) {
      if (!req.headers[authHeader]) {
        next();
        return;
      }
      var profile = req.profile;
      User.find({ where: { github: profile.id }}, function(err, users) {
        var user = users[0];
        if (user) {
          res.status(409).send({ message: 'There is already a GitHub account that belongs to you' });
          return;
        }
        var token = req.headers[authHeader].split(' ')[1];
        var payload = jwt.decode(token, config.TOKEN_SECRET);
        User.findById(payload.sub, function(err, user) {
          if (!user) {
            res.status(400).send({ message: 'User not found' });
            return;
          }
          user.github = profile.id;
          user.displayName = user.displayName || profile.name;
          user.save(function() {
            res.send({ 
              token: createToken(user),
              user: user
            });
          });
        });
      });
    }
docs: Step 3a. Link user accounts.