title: Yii2 Sort multiple parameters URL
body: <p>I have an endpoint in yii2 where I need to sort by multiple parameters. Im using ActiveDataProvider. This is the enpdoint: </p>
  
  <pre><code>public function actionIndex($client) 
  {
          $sort = new Sort([
              'attributes'=&gt; ['name','mail','crdate']
          ]);
          $query = Customer::find()
                  -&gt;andWhere(['client' =&gt; $client])
                  -&gt;orderBy($sort-&gt;orders);
          $provider = new ActiveDataProvider(['query' =&gt; $query]);
          return $provider-&gt;getModels();
  }
  </code></pre>
  
  <p>Now sorting by a single parameter as in: <strong>customers?client=1&amp;sort=mail</strong> works fine.</p>
  
  <p>I want to sort by multiple parameters though. How should I do this in the url?</p>