title: how to set default value to column in rails while creating migration
body: <p>I am new to Model in rails. I know how to create model &amp; how to add column to them. Now I want to set default value to a column but I am not getting that how exactly I can do it.</p>
  
  <p>I generated new model</p>
  
  <pre><code>rails g model User
  </code></pre>
  
  <p>then added column to it</p>
  
  <pre><code>rails generate migration AddNotificationEmailToUsers notification_email:boolean
  </code></pre>
  
  <p>Now I want to set value of Notification column default as true.
  Please guide me how to write the migration for the same. Thank you!!!</p>