Storage/S3: Move content disposition util to plugin

It was in the indico core because flask did not expose it and we needed
it there, but that's no longer the case (still not exposed though) so we
include it here now.

storage_s3/indico_storage_s3/storage.py

@@ -26,7 +26,9 @@ from indico.core.config import config
 from indico.core.storage import Storage, StorageError
 from indico.core.storage.backend import ReadOnlyStorageMixin, StorageReadOnlyError
 from indico.util.fs import get_file_checksum
-from indico.web.flask.util import make_content_disposition_args, send_file
+from indico.web.flask.util import send_file
+
+from indico_storage_s3.util import make_content_disposition_args
 
 
 s3_session_cache = threading.local()

storage_s3/indico_storage_s3/util.py

@@ -0,0 +1,22 @@
+# This file is part of the Indico plugins.
+# Copyright (C) 2002 - 2021 CERN
+#
+# The Indico plugins are free software; you can redistribute
+# them and/or modify them under the terms of the MIT License;
+# see the LICENSE file for more details.
+
+import unicodedata
+
+from werkzeug.urls import url_quote
+
+
+def make_content_disposition_args(attachment_filename):
+    try:
+        attachment_filename = attachment_filename.encode('ascii')
+    except UnicodeEncodeError:
+        return {
+            'filename': unicodedata.normalize('NFKD', attachment_filename).encode('ascii', 'ignore'),
+            'filename*': "UTF-8''%s" % url_quote(attachment_filename, safe=b''),
+        }
+    else:
+        return {'filename': attachment_filename}