title: Prevent two users from editing the same page at the same time
body: <p>I would like to prevent two users from being able to editing the same page at the same time. When one user is editing a page, the other users shall not be able to visit that page. My first thought was to just set a value in my database but to update that value using an ajax request would be useless if the users browser unintentionally shut down in any way.</p>
  
  <p>Is it possible to do this in a more secure/sustainable way?</p>