Add support for non-ASCII filenames in api_content_raw (option 2: copy FileResponse.set_headers)
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 !1096 (closed).
Migrated from D8109 (view on Phabricator)