title: After submit action in form_alter
body: <p>i need to insert data in my tables after user creation. I think to use <code>hook_form_alter()</code> for <code>$form_id == "user_register"</code> but I don't know how to say "after you created user, do this."</p>
  
  <p>How can I do it in <code>hook_form_alter()</code>?</p>