refactored to middleware

The better approach in ExpressJS is to author up a quick middleware you
can toss onto any route to short-circuit the rest fo the route with the
redirect.

The implementation submitted was actually running double output. The
"checkForUser" method would call `res.redirect`, return, and then the
method would continue and produce additional output.

Explicit middleware helps prevent those kinds of errors :)

app/controllers/welcome.js

@@ -23,23 +23,29 @@ class WelcomeController extends SiteController {
 
     captcha.loadFont(path.join(this.dtp.config.root, 'client', 'fonts', 'Dirty Sweb.ttf'));
 
+    function preventUserAccess (req, res, next) {
+      if (req.user) {
+        return res.redirect(301, '/');
+      }
+      return next();
+    }
+
     const router = express.Router();
     this.dtp.app.use('/welcome', welcomeLimiter, async (req, res, next) => {
       res.locals.currentView = 'welcome';
       return next();
     }, router);
 
-    router.get('/core-member', this.getWelcomeCoreMember.bind(this));
+    router.get('/core-member', preventUserAccess, this.getWelcomeCoreMember.bind(this));
     router.get('/signup/captcha', this.getSignupCaptcha.bind(this));
-    router.get('/signup', this.getSignupView.bind(this));
-    router.get('/login', this.getLoginView.bind(this));
-    router.get('/', this.getHomeView.bind(this));
+    router.get('/signup', preventUserAccess, this.getSignupView.bind(this));
+    router.get('/login', preventUserAccess, this.getLoginView.bind(this));
+    router.get('/', preventUserAccess, this.getHomeView.bind(this));
 
     return router;
   }
 
   async getWelcomeCoreMember (req, res) {
-    await this.checkForUser(req, res);
     res.render('welcome/core-member');
   }
 
@@ -59,33 +65,19 @@ class WelcomeController extends SiteController {
   }
 
   async getSignupView (req, res) {
-    await this.checkForUser(req, res);
     req.session.captcha = req.session.captcha || { };
     req.session.captcha.signup = captcha.randomText(4 + Math.floor(Math.random()*4));
     res.render('welcome/signup');
   }
 
   async getLoginView (req, res) {
-    await this.checkForUser(req, res);
     res.locals.loginResult = req.session.loginResult;
     res.render('welcome/login');
   }
 
-  async getHomeView (req, res, next) {
-    try {
-      await this.checkForUser(req, res);
-      res.render('welcome/index');
-    } catch (error) {
-      return next(error);
-    }
+  async getHomeView (req, res) {
+    res.render('welcome/index');
   }
- 
-  async checkForUser (req, res) {
-    if (req.user) {
-      res.redirect(301, '/');
-    }
-  }
-
 }
 
 module.exports = {