Configuration:
	config/passport.js
		// Set up passport strategy
		// Local Strategy in this case

		// Import modules
		const LocalStrategy = require('passport-local').Strategy;
		const bcrypt = require('bcryptjs');
		const User = require('../models/User');

		module.exports = (passport) => {
			// Local strategy
			passport.use(new LocalStrategy(
				// Use form fields different from the default of "username" and "password"
				{
					usernameField: 'email',
                    // passwordField: myPasswordField
				},

				function(email, password, done) {
					// Find the user if they exist
					User.findOne({ email: email }, (err, user) => {
						if (err) {
							return done(err);
						}
						if (!user) {
							return done(null, false, { message: 'Incorrect email and/or password.' });
						}
						// Check user password
						bcrypt.compare(password, user.password, (err, res) => {
							if (err) {
								return done(err);
							}
							if (!res) {
								return done(null, false, { message: 'Incorrect email and/or password.' });
							}
							return done(null, user);
						});
					});
				}
			));


			// Session configuration
			passport.serializeUser((user, done) => {
				done(null, user.id);
			});

			passport.deserializeUser((id, done) => {
				User.findById(id, done);
			});
		};


	config/general.js
		// General configuration file for the project
		// Takes app as a parameter where app=express();

		// import passport
		const passport = require('passport');

		// Passport middleware
		app.use(passport.initialize());
		app.use(passport.session());


	app.js
		const passport = require('passport');
		require('./config/general')(app);
			// The general configuration file
		require('./config/passport')(passport);
			// Configuration for passport strategy and sessions

// ----------------------------

Routes:
	User registration:
		Example form validation and sanitization with express-validator:
			body('name', 'Name is required').trim().isLength({min: 1}),
			body('email').trim()
				.isLength({min: 1}).withMessage('Email is required')
				.isEmail().withMessage('Incorrect format for email'),
			body('password')
				.isLength({min: 1}).withMessage('Password is required')
				.matches(/[^\s]/).withMessage('Must not contain any whitespace characters')
				.matches(/[a-zA-Z]/).withMessage('Must contain at least one letter'),
			body('password2')
				.exists()
				.custom((val, {req}) => val === req.body.password).withMessage('Passwords do not match'),
			sanitizeBody('name').trim().escape(),
			sanitizeBody('email').trim().normalizeEmail(),
			sanitizeBody('password').escape()

		Example errors and flash / page messages:
			// Get matched data from express-validator in variable user
			const user = matchedData(req);
			const errors = validationResult(req);

			// Some view stuff with displaying errors and re-rendering the registration form
			if (!errors.isEmpty()) {
				return res.render('users/register', {errors: errors.array({onlyFirstError: true}), name: user.name, email: user.email})
			}

		User registration POST route:
			// Check if email already exists
			User.findOne({email: user.email}, (err, registeredUser) => {
				if (err) {
					return next(err);
				}
				if (registeredUser) {
					req.flash('error_msg', 'This email has already been registered');
					return res.redirect('back');
				}
				let newUser = new User({
					name: user.name,
					email: user.email,
				});
				bcrypt.hash(user.password, 10, (err, hash) => {
					newUser.password = hash;
					newUser.save((err) => {
						if (err) {
							return next(err);
						}
						req.flash('success_msg', 'You are now registered');
						res.redirect('/users/login');

						// or login immediately
						/*
						req.login(newUser, (err) => {
							if (err) {
								return next(err);
							}
							return res.redirect('/ideas');
						});
						*/
					});
				});
			});

	User login POST route:
		// Feel free to add form validation as in the register route
		app.post('/login', passport.authenticate('local', {
			successRedirect: '/ideas',
			failureRedirect: '/users/login',
			failureFlash: true
		});

	User logout:
		app.get('/logout', (req, res) => {
			req.logout();
			res.redirect('/ideas');
		};

	User login / register GET routes:
        Just render a form for login and registration.