title: Get count from Objection.js query using withGraphJoined
body: <p>I have a really simple query and I'm trying to get the count.</p>
  
  <pre class="lang-js prettyprint-override"><code>const query = Product.query()
    .withGraphJoined('collections')
    .whereIn('collections.id', [1,3]);
  </code></pre>
  
  <p>I tried <code>resultSize()</code>, which worked on other queries I made that didn't use <code>withGraphJoined</code>. The only thing that works is if I do <code>count()</code> on the query, which returns the following:</p>
  
  <pre><code>Product {
    'count(*)': 6,
    id: 1,
    name: 'product',
    slug: 'slug',
    price: 32,
  }
  </code></pre>
  
  <p>Is there a cleaner way to do a total count on queries with <code>withGraphJoined</code>?</p>