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/routing.yaml

@@ -0,0 +1,7 @@
+framework:
+    router:
+        utf8: true
+
+        # Configure how to generate URLs in non-HTTP contexts, such as CLI commands.
+        # See https://symfony.com/doc/current/routing.html#generating-urls-in-commands
+        #default_uri: http://localhost