title: Select rows having 2 columns equal value in laravel Query builder
body: <p>I want to write a query which selects rows where 2 attributes from 1 entity have equal value.</p>
  
  <p>This would be an example of doing this in raw SQL: </p>
  
  <pre><code>Select * from users u where u.username = u.lastname
  </code></pre>
  
  <p>Does laravel have any methods that take 2 column names as parameters and return the matching results?</p>