Value of Content-Disposition header:

Content-Disposition: attachment; filename*=UTF-8''foo-%c3%a4.html; filename="foo-ae.html"

Test Description:

'attachment', specifying a filename of foo-ae.html in the traditional format, and foo-.html in RFC2231 format.

Section 4.2 of RFC 5987 and Section 4.3 of RFC 6266 suggest that the RFC 2231/5987 encoded parameter ("filename*") should take precedence when understood.