Magento 2 – Extending Catalog Module Class Not Working

I am working on a module that is meant to extend \Magento\Catalog\Model\Category in order to get the thumbnail URL. I based the code on getImageUrl in the base class. I have my main Model file CategoryThumbnail.php: <?php namespace Module\CategoryThumbnail\Model; use Magento\Authorization\Model\UserContextInterface; use Magento\Catalog\Api\CategoryRepositoryInterface; use Magento\Catalog\Api\Data\CategoryInterface; use Magento\CatalogUrlRewrite\Model\CategoryUrlRewriteGenerator; use Magento\Framework\Api\AttributeValueFactory; use Magento\Framework\App\ObjectManager; use Magento\Framework\AuthorizationInterface; use Magento\Framework\Convert\ConvertArray;…