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/packages/framework.yaml

@@ -0,0 +1,24 @@
+# see https://symfony.com/doc/current/reference/configuration/framework.html
+framework:
+    translator:
+        enabled: true
+        fallback: "%env(LOCALE)%"
+        default_path: '%kernel.project_dir%/translations'
+    secret: '%env(APP_SECRET)%'
+    router:
+        strict_requirements: ~
+    form: ~
+    csrf_protection: ~
+    validation:
+        enable_annotations: true
+    templating:
+        engines: ['twig']
+    default_locale: "%env(LOCALE)%"
+    trusted_hosts: ~
+    session:
+        # handler_id set to null will use default session handler from php.ini
+        handler_id: session.handler.native_file
+        save_path: "%kernel.project_dir%/var/sessions/%kernel.environment%"
+    fragments: ~
+    http_method_override: true
+    assets: ~