refactor: add phpstan and update code to adhere to level 5

- move and refactor Image.php from Libraries to Entities folder
- update some database field names
/ types
- update composer packages

app/Controllers/FeedController.php

@@ -0,0 +1,65 @@
+<?php
+
+/**
+ * @copyright  2020 Podlibre
+ * @license    https://www.gnu.org/licenses/agpl-3.0.en.html AGPL3
+ * @link       https://castopod.org/
+ */
+
+namespace App\Controllers;
+
+use CodeIgniter\HTTP\ResponseInterface;
+use CodeIgniter\Exceptions\PageNotFoundException;
+use Opawg\UserAgentsPhp\UserAgentsRSS;
+use Exception;
+use App\Models\EpisodeModel;
+use App\Models\PodcastModel;
+use CodeIgniter\Controller;
+
+class FeedController extends Controller
+{
+    public function index(string $podcastName): ResponseInterface
+    {
+        helper('rss');
+
+        $podcast = (new PodcastModel())->where('name', $podcastName)->first();
+        if (!$podcast) {
+            throw PageNotFoundException::forPageNotFound();
+        }
+
+        $service = null;
+        try {
+            $service = UserAgentsRSS::find($_SERVER['HTTP_USER_AGENT']);
+        } catch (Exception $exception) {
+            // If things go wrong the show must go on and the user must be able to download the file
+            log_message('critical', $exception);
+        }
+
+        $serviceSlug = null;
+        if ($service) {
+            $serviceSlug = $service['slug'];
+        }
+
+        $cacheName =
+            "podcast#{$podcast->id}_feed" . ($service ? "_{$serviceSlug}" : '');
+
+        if (!($found = cache($cacheName))) {
+            $found = get_rss_feed($podcast, $serviceSlug);
+
+            // The page cache is set to expire after next episode publication or a decade by default so it is deleted manually upon podcast update
+            $secondsToNextUnpublishedEpisode = (new EpisodeModel())->getSecondsToNextUnpublishedEpisode(
+                $podcast->id,
+            );
+
+            cache()->save(
+                $cacheName,
+                $found,
+                $secondsToNextUnpublishedEpisode
+                    ? $secondsToNextUnpublishedEpisode
+                    : DECADE,
+            );
+        }
+
+        return $this->response->setXML($found);
+    }
+}