express + passport-twitter でメールアドレスを取得するには

expressとpassportでユーザー認証を行う際、passport-twitterなどの使ってSNSアカウントで認証できるようなWebアプリを作っています。この中で、登録されているユーザーにメールで情報を配信したいと思っています。

そこでご質問ですが、メールアドレスはどのように取得するのが順当な方法でしょうか？例えばユーザーがtwitterアカウントで認証した際に、メールアドレスを登録するような処理が改めて必要になってくるのでしょうか？

ご存知な方がいらっしゃいましたら、アドバイスを宜しくお願いします。

コードはExpress4 + Passport を使った会員サイトの簡単サンプル | try catch and ...releaseを参考にしながら、tiwtter認証を追加しているところです。

package.json

{
  "name": "passport-express4-sample",
  "version": "0.0.0",
  "private": true,
  "scripts": {
    "start": "node ./bin/www",
    "test": "./node_modules/mocha/bin/mocha ./test/test.user.js"
  },
  "dependencies": {
    "body-parser": "~1.13.2",
    "chai": "*",
    "cookie-parser": "~1.3.5",
    "debug": "~2.2.0",
    "express": "~4.13.1",
    "express-session": "*",
    "jade": "~1.11.0",
    "mocha": "*",
    "mongoose": "*",
    "morgan": "~1.6.1",
    "passport": "*",
    "passport-local": "*",
    "passport-local-mongoose": "*",
    "passport-twitter": "^1.0.3",
    "serve-favicon": "~2.3.0",
    "should": "*"
  }
}

./app.js

var TWITTER_CONSUMER_KEY      = "*** your key ***";
var TWITTER_CONSUMER_SECRET   = "*** your secret key ***";
var BASE_URL                  = "*** your url ***";

var express      = require('express');
var path         = require('path');
var favicon      = require('serve-favicon');
var logger       = require('morgan');
var cookieParser = require('cookie-parser');
var bodyParser   = require('body-parser');
var session      = require('express-session');
var mongoose      = require('mongoose');
var passport      = require('passport');
var LocalStrategy = require('passport-local').Strategy;
var TwitterStrategy = require('passport-twitter').Strategy;


var routes = require('./routes/index');
var users  = require('./routes/users');
var app    = express();
app.set('views', path.join(__dirname, 'views'));
app.set('view engine', 'jade');


app.use( logger('dev') );
app.use( bodyParser.json() );
app.use( bodyParser.urlencoded({ extended: false }) );
app.use( cookieParser() );

app.use(session({
  secret: 'secret secret' ,
  resave: false ,
  saveUninitialized: false
}));
app.use( passport.initialize() );
app.use( passport.session() );


app.use(express.static(path.join(__dirname, 'public')));
app.use('/', routes);
app.use('/users', users);


var Account = require('./models/account');
passport.use( new LocalStrategy(Account.authenticate()) );
passport.serializeUser( Account.serializeUser() );
passport.deserializeUser( Account.deserializeUser() );
mongoose.connect('mongodb://localhost/passport_local_mongoose_express4');

passport.use( new TwitterStrategy({
        consumerKey: TWITTER_CONSUMER_KEY,
        consumerSecret: TWITTER_CONSUMER_SECRET,
        callbackURL: BASE_URL+'/auth/twitter/callback'
    },
    function(token, tokenSecret, profile, done) {

        var acc = new Account();
        acc.username          = profile.username;
        acc.password          = "";
        acc.twitter.id        = profile.id;

        acc.save(function(err) {
            if (err)throw err;
            return done(null,acc);
        });
    }
));

app.get('/auth/twitter' , passport.authenticate('twitter') );
app.get('/auth/twitter/callback', passport.authenticate('twitter', {
        failureRedirect: '/'
    }),
    function(req, res) {
        res.redirect('/');
    }
);

// catch 404 and forward to error handler
app.use(function(req, res, next) {
  var err = new Error('Not Found');
  err.status = 404;
  next(err);
});

// development error handler
// will print stacktrace
if (app.get('env') === 'development') {
  app.use(function(err, req, res, next) {
    res.status(err.status || 500);
    res.render('error', {
      message: err.message,
      error: err
    });
  });
}

// production error handler
// no stacktraces leaked to user
app.use(function(err, req, res, next) {
  res.status(err.status || 500);
  res.render('error', {
    message: err.message,
    error: {}
  });
});

module.exports = app;

./models/account.js

var mongoose              = require('mongoose');
var Schema                = mongoose.Schema;
var passportLocalMongoose = require('passport-local-mongoose');

var Account = new Schema({
          username: String ,
          password: String ,
          twitter : {
            id: String
        }
});

Account.plugin(passportLocalMongoose);
module.exports = mongoose.model('Account', Account);