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.

config/preload.php

@@ -0,0 +1,9 @@
+<?php
+
+if (file_exists(dirname(__DIR__) . '/var/cache/prod/srcApp_KernelProdContainer.preload.php')) {
+    require dirname(__DIR__) . '/var/cache/prod/srcApp_KernelProdContainer.preload.php';
+}
+
+if (file_exists(dirname(__DIR__) . '/var/cache/prod/App_KernelProdContainer.preload.php')) {
+    require dirname(__DIR__) . '/var/cache/prod/App_KernelProdContainer.preload.php';
+}