feat: Implement the /user/me endpoint

frontend/src/components/app.tsx

@@ -36,15 +36,37 @@ interface IProps {
 // TODO: Replace the sessionStorage with localStorage?
 export default class Application extends React.Component<IProps> {
     componentDidMount() {
-        // TODO: Ask the server if our session is still valid
         // TODO: When asking the server if our session is still valid, a spinner
         //       should be shown
-        if (getSessionToken(window) !== null) {
-            // TODO: We still need to fetch the user data
-            this.props.setAuthenticated(true);
+        const token = getSessionToken(window);
+        if (token !== null && !this.props.authenticated) {
+            this.checkAuthStatus(token).then(user => {
+                this.props.setUser(user);
+                this.props.setAuthenticated(true);
+            }).catch(err => {
+                this.props.setAuthenticated(false);
+            });
         }
     }
 
+    checkAuthStatus = (token: string): Promise<IUser> => {
+        return new Promise((res, rej) => {
+            fetch(`${BACKEND_URL}/api/user/me`, {
+                headers: new Headers({
+                    "Content-Type": "application/json",
+                    "Token": token,
+                }),
+            }).then(resp => resp.json(), err => rej(err))
+                .then(data => {
+                    if (data.error === "0") {
+                        res(data.data);
+                    } else {
+                        rej(data);
+                    }
+                });
+        });
+    }
+
     getLevels = (): Promise<ILevel[]> => {
         return new Promise((res, rej) => {
             fetch(`${BACKEND_URL}/api/levels`, {

frontend/src/reducers/index.ts

@@ -68,7 +68,6 @@ const initialState: IState = {
     didLogin: false,
 
     // Is the user authenticated?
-    // TODO: Set this to false
     authenticated: false,
 
     user: {