Hi, thanks your great work!

I have a trouble to validate requests in multipart/form-data format; requests have parts without Content-Type Header, but validation refused them.

multipart requests

According to HTML Living Standard, Content-Type Header of parts of multipart/form-data must be removed in specific patterns.

The parts of the generated multipart/form-data resource that correspond to non-file fields must not have a Content-Type header specified.
https://html.spec.whatwg.org/multipage/form-control-infrastructure.html#multipart-form-data

like this:

Content-Type: multipart/form-data; boundary=XXXXX; 
...
--XXXXX
Content-Disposition: form-data; name="id"

123
--XXXXX
Content-Disposition: form-data; name="image"; filename="sample.png"
Content-Type: image/png
...
--XXXXX

image has Content-Type Header, but id doesn't.

validation

Now multipartBodyDecoder depends on decodeBody function,

and decodeBody returns an error when the part has no Content-Type header.