refactor(app.js, auth.js): Extract all auth method to individual modules

lib/web/auth/github/index.js

@@ -0,0 +1,28 @@
+'use strict'
+
+const Router = require('express').Router
+const passport = require('passport')
+const GithubStrategy = require('passport-github').Strategy
+const config = require('../../../config')
+const {setReturnToFromReferer, passportGeneralCallback} = require('../utils')
+
+let githubAuth = module.exports = Router()
+
+passport.use(new GithubStrategy({
+  clientID: config.github.clientID,
+  clientSecret: config.github.clientSecret,
+  callbackURL: config.serverurl + '/auth/github/callback'
+}, passportGeneralCallback))
+
+githubAuth.get('/auth/github', function (req, res, next) {
+  setReturnToFromReferer(req)
+  passport.authenticate('github')(req, res, next)
+})
+
+// github auth callback
+githubAuth.get('/auth/github/callback',
+  passport.authenticate('github', {
+    successReturnToOrRedirect: config.serverurl + '/',
+    failureRedirect: config.serverurl + '/'
+  })
+)