add and use isAuthenticated method

src/lib/authentication.js

@@ -1,3 +1,7 @@
 export function getUser() {
   return Promise.resolve(null);
 }
+
+export function isAuthenticated() {
+  return getUser().then(Boolean);
+}

src/pages/Login.vue

@@ -22,7 +22,7 @@
 </template>
 
 <script>
-  import { getUser } from '../lib/authentication';
+  import { isAuthenticated } from '../lib/authentication';
   import TopNav from '../components/TopNav.vue';
 
   export default {
@@ -43,7 +43,7 @@
         return { name: 'customers' };
       }
 
-      return getUser().then(user => {
+      return isAuthenticated().then(user => {
         const sendTo = getRedirect();
         // if already logged in, redirect
         if (user) return next(sendTo);

src/router.js

@@ -8,7 +8,7 @@ import Customers from './pages/Customers.vue';
 import Orders from './pages/Orders.vue';
 import About from './pages/About.vue';
 
-import { getUser } from './lib/authentication';
+import { isAuthenticated } from './lib/authentication';
 
 Vue.use(VueRouter);
 
@@ -51,7 +51,7 @@ const router = new VueRouter({
 router.beforeEach((to, from, next) => {
   // check if any of the matched routes require authentication
   if (to.matched.some(record => record.meta.requiresAuthentication)) {
-    return getUser().then((user) => {
+    return isAuthenticated().then((user) => {
       // if user is authenticated, continue
       if (user) return next();