POST multipart/form-data fails on HTTP/2

[ldav1s]

Running Cro::HTTP 0.8.11 (though also reproduced on 0.8.10) on rakudo:

$ raku --version
Welcome to Rakudo™ v2024.06.
Implementing the Raku® Programming Language v6.d.
Built on MoarVM version 2024.06.

on Ubuntu:

$ lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description:    Ubuntu 20.04.6 LTS
Release:        20.04
Codename:       focal

This isn't the exactly code matching the CRO_TRACE dumps, but is very close, and I think I've actually reproduced it with this code, even though my HTTP/2 server (running on 9999) wasn't configured quite right.

 #!/usr/bin/env raku
use v6;
use Cro::HTTP::Client;

sub MAIN () {
    my $sr_key_yml = "SR: SR-whatever\n";
    my @parts;
    my $part = Cro::HTTP::Body::MultiPartFormData::Part.new(
        name => 'file',
        filename => "sr-key.yml",
        body-blob => $sr_key_yml.encode('utf-8'),
        headers => [Cro::HTTP::Header.new(name => 'Content-type', value => 'application/yaml')],
    );
    @parts.push($part);
    my $multipart-body = Cro::HTTP::Body::MultiPartFormData.new(:@parts);
    my $resp = await Cro::HTTP::Client.post: "http://localhost:9999/",
            headers => [accept => 'application/json', X-Atlassian-Token => 'no-check'],
            body => $multipart-body, http => 2;
}

The code I actually am concerned about doesn't select http => 2 as a parameter, but Cro::HTTP::Client does that automatically.

When I run that code I get something like this output from CRO_TRACE which returns a 415 from the server:

cro-client-http-2-multipart.txt

When I set http => 1.1 as an option, the server returns 200 and CRO_TRACE looks like:

cro-client-http1.1-multipart.txt

[ldav1s]

What I suspect (but I'm not sure) is that the Content-type isn't being set correctly (or at all) for HTTP/2, hence the 415.