title: How to edit additional data in HABTM tables?
body: <p>How do I update additional data in HABTM tables.</p>
  
  <p>For Example: I have <code>movies</code>, <code>people</code> and HABTM <code>movies_people</code> tables, but there is additional <code>persontype_id</code> field in <code>movies_people</code> table which indicates role of this person in that particular movie. How do I add/change this value?</p>