Custom Preview Target for Craft 3.2

Module.php

<?php

// -- modules/Module.php --

namespace modules;

use Craft;
use craft\base\Element;
use craft\elements\Entry;
use craft\events\RegisterPreviewTargetsEvent;
use craft\events\RegisterUrlRulesEvent;
use craft\helpers\UrlHelper;
use craft\web\UrlManager;
use yii\base\Event;

class Module extends \yii\base\Module
{
    /**
     * Initializes the module.
     */
    public function init()
    {
        // Set a @modules alias pointed to the modules/ directory
        Craft::setAlias('@modules', __DIR__);

        // Set the controllerNamespace based on whether this is a console or web request
        if (Craft::$app->getRequest()->getIsConsoleRequest()) {
            $this->controllerNamespace = 'modules\\console\\controllers';
        } else {
            $this->controllerNamespace = 'modules\\controllers';
        }

        parent::init();

        Event::on(UrlManager::class, UrlManager::EVENT_REGISTER_SITE_URL_RULES, function(RegisterUrlRulesEvent $e) {
            $e->rules['test-target'] = 'module/test/test';
        });

        Event::on(Entry::class, Entry::EVENT_REGISTER_PREVIEW_TARGETS, function(RegisterPreviewTargetsEvent $e) {
            /** @var Element $element */
            $element = $e->sender;
            $e->previewTargets[] = [
                'label' => 'Test',
                'url' => UrlHelper::siteUrl('test-target', [
                    'elementId' => $element->id,
                    'siteId' => $element->siteId,
                ]),
            ];

            // Do this if you want to protect the preview target from public access:
            Craft::$app->getSession()->authorize('customAuthorziationKey:' . $element->id);
        });
    }
}

TestController.php

<?php

// -- modules/controllers/TestController.php --

namespace modules\controllers;

use craft\base\Element;
use craft\web\Controller;

class TestController extends Controller
{
    public function actionTest(int $elementId, int $siteId)
    {
        // Do this if you want to protect the preview target from public access:
        $this->requireAuthorization('customAuthorizationKey:' . $elementId);

        /** @var Element $element */
        $element = \Craft::$app->getElements()->getElementById($elementId, null, $siteId);
        return $this->asRaw($element->title);
    }
}