Add NOT_SECURED and newrelic stub

Set NOT_SECURED=true in postiz install script for local/non-secured setups. In simplelogin install, detect the venv site-packages path and create a minimal newrelic package stub (newrelic/__init__.py and newrelic/agent.py) with no-op record_custom_event and initialize functions to avoid import errors when New Relic is not present.

install/postiz-install.sh

@@ -45,6 +45,7 @@ MAIN_URL=http://${LOCAL_IP}
 FRONTEND_URL=http://${LOCAL_IP}
 NEXT_PUBLIC_BACKEND_URL=http://${LOCAL_IP}/api
 BACKEND_INTERNAL_URL=http://localhost:3000
+NOT_SECURED=true
 TEMPORAL_ADDRESS=localhost:7233
 IS_GENERAL=true
 STORAGE_PROVIDER=local