title: Disable devise's :confirmable on-the-fly to batch-generate users
body: <p><a href="https://github.com/plataformatec/devise" rel="noreferrer">Devise</a> is a Ruby library that provides me with this <code>User</code> class:</p>
  
  <pre><code>class User &lt; ActiveRecord::Base
    has_many :user_tokens
    devise :trackable, :confirmable
  </code></pre>
  
  <p>When <code>:confirmable</code> is written, a confirmation email is sent upon registration.</p>
  
  <p>Last week I had to batch-create 300 users, so I commented out <code>:confirmable</code> for a few minutes before reverting.</p>
  
  <p>Now I am creating a UI for user batch-creation, so I need to add/remove <code>:confirmable</code> on-the-fly. (I could also modify Devise's source code directly but I would rather not temper with it)</p>
  
  <p><b>QUESTION:</b> How to add/remove <code>:confirmable</code> on-the-fly?</p>