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/Version20200414120227.php

@@ -0,0 +1,23 @@
+<?php
+
+namespace DoctrineMigrations;
+
+use App\Doctrine\WallabagMigration;
+use Doctrine\DBAL\Migrations\SkipMigrationException;
+use Doctrine\DBAL\Schema\Schema;
+
+/**
+ * Remove baggy theme.
+ */
+final class Version20200414120227 extends WallabagMigration
+{
+    public function up(Schema $schema): void
+    {
+        $this->addSql('UPDATE ' . $this->getTable('config', true) . " SET theme = 'material';");
+    }
+
+    public function down(Schema $schema): void
+    {
+        throw new SkipMigrationException('Not possible ... ');
+    }
+}