Error messages for invalid tokens from email links

This commit, adds error messages for users hiting the confirm
endpoint with invalid, or expired tokens from emailed links.

common/models/user.js

@@ -90,13 +90,66 @@ module.exports = function(User) {
   });
 
   debug('setting up user hooks');
+
+  User.beforeRemote('confirm', function(ctx, _, next) {
+
+    if (!ctx.req.query) {
+      return ctx.res.redirect('/');
+    }
+
+    const uid = ctx.req.query.uid;
+    const token = ctx.req.query.token;
+    const redirect = ctx.req.query.redirect;
+
+    return User.findById(uid, (err, user) => {
+
+        if (err || !user) {
+          ctx.req.flash('error', {
+            msg: dedent`Oops, something went wrong, please try again later`
+          });
+          return ctx.res.redirect('/');
+        }
+
+        if (!user.verificationToken && !user.emailVerified) {
+          ctx.req.flash('info', {
+            msg: dedent`Looks like we have your email. But you haven't
+             verified it yet, please login and request a fresh verification
+             link.`
+          });
+          return ctx.res.redirect(redirect);
+        }
+
+        if (!user.verificationToken && user.emailVerified) {
+          ctx.req.flash('info', {
+            msg: dedent`Looks like you have already verified your email.
+             Please login to continue.`
+          });
+          return ctx.res.redirect(redirect);
+        }
+
+        if (user.verificationToken && user.verificationToken !== token) {
+          ctx.req.flash('info', {
+            msg: dedent`Looks like you have clicked an invalid link.
+             Please login and request a fresh one.`
+          });
+          return ctx.res.redirect(redirect);
+        }
+
+        return next();
+    });
+  });
+
   User.afterRemote('confirm', function(ctx) {
+    if (!ctx.req.query) {
+      return ctx.res.redirect('/');
+    }
+    const redirect = ctx.req.query.redirect;
     ctx.req.flash('success', {
       msg: [
         'Your email has been confirmed!'
       ]
     });
-    ctx.res.redirect('/');
+    return ctx.res.redirect(redirect);
   });
 
   User.beforeRemote('create', function({ req, res }, _, next) {