def pick_username(ideal)
      name = ideal
      i = 0

      while user_exists?(name)
        i += 1
        name = "#{ideal}_#{i}"
      end

      name
    end
def pick_username(ideal)
      name = ideal
      i = 0

      while user_exists?(name)
        i += 1
        name = "#{ideal}_#{i}"
      end

      name
    end
Pick a username that does not yet exist on the system. If the given
 username does not exist, it is returned; else we add a "_1" suffix
 and continue incrementing the number until we arrive at a username
 that does not yet exist.

 === Parameters
 ideal(String):: the user's ideal (chosen) username

 === Return
 username(String):: username with possible postfix