FIX: setup permission check based on group membership.

former permission check, based on django model permission won't work,
because we have no model, that would create the permission.

dav_submission/django_project_config/settings-dav_submission.py

@@ -8,4 +8,5 @@ from django.conf import settings
 # MAX_FILE_SIZE_MIB = 50
 # MAX_TOTAL_SIZE_MIB = 100
 # METADATA_FILE_NAME = 'metadata.txt'
-# CACHED_ZIP_FILE_NAME = '.cache.zip'
+# CACHED_ZIP_FILE_NAME = '.cache.zip'
+# DOWNLOAD_GROUP = 'downloaders'