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/test/framework.yaml

@@ -0,0 +1,10 @@
+framework:
+    test: ~
+    session:
+        storage_id: session.storage.mock_file
+    profiler:
+        collect: false
+    translator:
+        enabled: false
+    mailer:
+        dsn: 'null://null'