title: Get all URL used by routes in Symfony 2
body: <p>I'm working on a website using Symfony 2 in which each user will have a profile page reachable at <code>domain.com/username</code> (like many social websites offer).</p>
  
  <p>To achieve this I need to check if the wanted URL is available when a user wants to pick one.
  I would like to know if there is a way in Symfony to get all URL used by routes defined in routing configuration to automatically forbid those routes as usernames.</p>
  
  <p>Thank you</p>