Move to Symfony Flex

The structure changed completely.
Bundles are gone. Everything is flatten in the folder `src`.
I separated import & api controllers to avoid _pollution_ in the main controller folder.

migrations/Version20230613121354.php

@@ -0,0 +1,30 @@
+<?php
+
+namespace Application\Migrations;
+
+use Doctrine\DBAL\Schema\Schema;
+use Wallabag\CoreBundle\Doctrine\WallabagMigration;
+
+/**
+ * Added a new setting to display or not thumbnails.
+ */
+final class Version20230613121354 extends WallabagMigration
+{
+    public function up(Schema $schema): void
+    {
+        $configTable = $schema->getTable($this->getTable('config'));
+
+        $this->skipIf($configTable->hasColumn('display_thumbnails'), 'It seems that you already played this migration.');
+
+        $configTable->addColumn('display_thumbnails', 'integer', [
+            'default' => 1,
+            'notnull' => false,
+        ]);
+    }
+
+    public function down(Schema $schema): void
+    {
+        $configTable = $schema->getTable($this->getTable('config'));
+        $configTable->dropColumn('display_thumbnails');
+    }
+}