title: SPRING: Add custom user details to spring security user
body: <p>I'm currently working on a Spring MVC application and I need to add a custom field to my Spring Security log-in user right when I log in (I insert username, password, custom value).
  This value needs to be available on everywhere when the user is logged in (e.g. via pricipal.getValue).</p>
  
  <p>I read a lot about custom user classes and custom services, but can't really find a working solution for my problem...</p>
  
  <p>Any help would be great!</p>