title: Generate uniq username using first and last name in django
body: <p>I need to dynamically generate uniqe username during user's registartion.</p>
  
  <p>Algorithm:</p>
  
  <p>when user's full name is "John Doe" username should be "jdoe" (if available).
  If not, it should generate jdoe1, jdoe2 and so until username will be available.</p>
  
  <p>Any exisiting simple solution for this?</p>