title: UpdateExistingPivot for multiple ids
body: <p>In order to update single record in pivot table I use <code>updateExistingPivot</code> method. However it takes $id as the first argument. For example:</p>
  
  <pre><code>$step-&gt;contacts()-&gt;updateExistingPivot($id, [
      'completed' =&gt; true,
      'run_at' =&gt; \Carbon\Carbon::now()-&gt;toDateTimeString()
  ]);
  </code></pre>
  
  <p>But how can I update multiple existing rows in pivot table at once?</p>