Add support for non-ASCII filenames in api_content_raw (option 1: use FileResponse)
without either RFC5987/6266-encoding of the filename or RFC2231-encoding of the header, gunicorn crashes when trying to decode the header as ASCII.
Resolves #4388 (closed)
This is an alternative implementation of D8109.
Migrated from D8108 (view on Phabricator)