title: Symfony2 redirect /admin/* to /admin/login when not logged in (or use FOSUserBundle?)
body: <p>I am new to Symfony and I am trying to build an admin interface.  I have an existing users table and all I want is to secure the <code>^/admin.+</code> path with a login page at <code>/admin/login</code> and Symfony seems to be very tutorial-oriented with little explanation on how to customize anything. (or at least, not much info on how each piece component works together with the others)</p>
  
  <p>Here is my security.yml</p>
  
  <pre><code>encoders:
      AppBundle\Entity\Users:
          algorithm:        sha1
          encode_as_base64: false
          iterations:       1
  
  role_hierarchy:
      ROLE_ADMIN:       ROLE_USER
      ROLE_SUPER_ADMIN: [ ROLE_USER, ROLE_ADMIN, ROLE_ALLOWED_TO_SWITCH ]
  
  providers:
      administrators:
          entity: { class: AppBundle:Users, property: email }
      in_memory:
          memory: ~
  
  firewalls:
      dev:
          pattern: ^/(_(profiler|wdt)|css|images|js)/
          security: false
  
      main:
          anonymous: ~
  
      admin_area:
          pattern:    ^/admin
          anonymous:  ~
          provider:   administrators
          form_login:
              default_target_path: /admin
              check_path: /admin/login_check
              login_path: /admin/login
              remember_me: true
          logout:
              path:   /admin/logout
              target: /admin
  
  access_control:
      - { path: ^/admin/login, roles: IS_AUTHENTICATED_ANONYMOUSLY }
      - { path: ^/admin, roles: ROLE_ADMIN }
  </code></pre>
  
  <p>When I go to /admin I get error page with "Full authentication is required to access this resource."  What I want is for the app to redirect from <code>/admin/*</code> (except /admin/login of course) to <code>/admin/login</code> when not logged in.</p>
  
  <p><strong>Notes &amp; Other Questions</strong>  </p>
  
  <p>Symfony seems to want you to <em>always</em> use certain existing bundles and I have scoured the web for info on how to understand what's actually happening but only seem to find more and more tutorials.</p>
  
  <p>Should I even be using FOSUserBundle?  If so, can I use my existing users table or do I have to use their schema?</p>