feat: feature flags for sanitizing and stamping of uploads

composer.json

@@ -19,6 +19,7 @@
         "doctrine/doctrine-bundle": "^2.10",
         "doctrine/doctrine-migrations-bundle": "^3.2",
         "doctrine/orm": "^2.15",
+        "flagception/flagception-bundle": "^6.0",
         "knplabs/knp-menu-bundle": "^3.2",
         "knplabs/knp-paginator-bundle": "^6.2",
         "liip/imagine-bundle": "^2.11",