title: Ignore username's case in SpringSecurity
body: <p>Does SpringSecurity have some built-in ability to ignore the letter-case of username? For example, if the username is "student001", then it will accept "Student001" as well as "stUdent001".</p>
  
  <p>The reason I need this is that our system use emails as usernames. Of course I would be able to do this by extending the DAOAuthenticationProvider class, but I just wonder if there's any built-in option exists for this problem?</p>