Character outside of permitted range in Content Disposition

[bclozel]

There is a potential regression in the ContentDisposition header support. See #36328 (comment)

[bclozel]

After digging into this, I don't think this is strictly a regression. Before #36328, the filename parameter was encoded using the RFC 2047 mechanism. As noted in #36328, this parameter should not be encoded but instead should use ISO-8859-1. But as noted in RFC 6266 Appendix D:

Avoid using non-ASCII characters in the filename parameter. Although most existing implementations will decode them as
ISO-8859-1, some will apply heuristics to detect UTF-8, and thus might fail on certain names.

I guess this is what triggered the reported problem. Let's apply the recommendations here and use ASCII strictly for the filename parameter and try to transliterate characters when possible and use _ as a fallback.