Percent encoding of content-disposition parameter values

[rollandjb]

There seems to be a problem with how reqwest encodes values of Content-Disposition parameters.

RFC 6266 and RFC 8187 defines the characters that can be included without percent encoding in an encoded value of a Content-Disposition parameter as

 attr-char  = ALPHA / DIGIT
              / "!" / "#" / "$" / "&" / "+" / "-" / "."
              / "^" / "_" / "`" / "|" / "~"

which is to say

 a-zA-Z0-9!#$&+-.^_`|~

Reqwest uses PATH_SEGMENT_ENCODE_SET from the url crate to encode parameter values, which in addition allows the following characters

 '(),=@[\]

This causes problems when files having any of these characters in their names are uploaded to servers that rely on the RFC

[yageek]

Sorry for polluting the history with bad commits :( I had some issues with my network and keyboard...