// uses auth.service to check if user has token in storage. Returns true if there is a token
// returns false if user does not have a token and navigates to initial login page.
canActivate(route: ActivatedRouteSnapshot): Observable<boolean> {
  return this.auth.user.pipe(
    take(1),
    map(user => {
      console.log('Can activate: ', user);
      if (!user) {
        this.alertCtrl.create({
          header: 'Unauthorized',
          message: 'You are not allowed to access that page.',
          buttons: ['OK']
        }).then(alert => alert.present());

        this.router.navigateByUrl('/');
        return false;
      } else {
        return true;
      }
    })
  );
}