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/Version20221123132612.php

@@ -0,0 +1,32 @@
+<?php
+
+namespace DoctrineMigrations;
+
+use App\Doctrine\WallabagMigration;
+use Doctrine\DBAL\Schema\Schema;
+
+/**
+ * Drop theme fields from config table.
+ */
+final class Version20221123132612 extends WallabagMigration
+{
+    public function up(Schema $schema): void
+    {
+        $configTable = $schema->getTable($this->getTable('config'));
+
+        $this->skipIf(!$configTable->hasColumn('theme'), 'It seems that you already played this migration.');
+
+        $configTable->dropColumn('theme');
+    }
+
+    public function down(Schema $schema): void
+    {
+        $configTable = $schema->getTable($this->getTable('config'));
+
+        $this->skipIf($configTable->hasColumn('theme'), 'It seems that you already played this migration.');
+
+        $configTable->addColumn('theme', 'string', [
+            'notnull' => true,
+        ]);
+    }
+}