title: Turn off "updated_at" column in Rails
body: <p>I have a simple "Log" model, that records the fact of calling controller's action.</p>
  
  <p>Entries of this "log" record are supposed to be created once and never altered. Also, I will have many of these records in the database.</p>
  
  <p>So, there is no need for "updated_at" column (don't need to waste the memory on HDD).</p>
  
  <p>How can I tell to Rails to leave only "created_at" column and not to use "updated_at"?</p>
  
  <p>Is there any way to make the "Log" model read only?</p>