title: custom primaryKey not working laravel 5.4
body: <p>Using Laravel 5.4.13, I have a model called Widget, where I set the primary key like this:</p>
  
  <pre><code>protected $primaryKey = 'widget_id';
  </code></pre>
  
  <p>The widgets table has a primary key column, int, auto-increment, named: widget_id.</p>
  
  <p>Yet, when I try to update a record on the browser I get this error:</p>
  
  <p>QueryException in Connection.php line 647:</p>
  
  <p>SQLSTATE[42S22]: Column not found: 1054 Unknown column 'id' in 'where clause' (SQL: select count(*) as aggregate from <code>widgets</code> where <code>name</code> = est eum and <code>id</code> &lt;> 3)</p>
  
  <p>It still looks for a column called: id and not widget_id.</p>
  
  <p>I found out it happens on this validation:</p>
  
  <pre><code>$this-&gt;validate($request, [
          'name' =&gt; 'required|string|max:40|unique:widgets,name,' .$widget-&gt;widget_id
      ]);
  </code></pre>
  
  <p>What am I missing?</p>