Introduce multipart encoder

[veewee]

Q	A
Type	feature
BC Break	no
Fixed issues

Summary

This PR allows for sending multipart form messages, uploads, mixed multi-parts, ... based on the parts available inside symfony/mime.

use Phpro\HttpTools\Encoding\Json\JsonDecoder;
use Phpro\HttpTools\Encoding\Mime\MultiPartEncoder;
use Phpro\HttpTools\Transport\EncodedTransportFactory;
use Symfony\Component\Mime\Part\DataPart;
use Symfony\Component\Mime\Part\Multipart\FormDataPart;
use Phpro\HttpTools\Request\Request;

$transport = EncodedTransportFactory::create(
    $client,
    $uriBuilder,
    MultiPartEncoder::createWithAutodiscoveredPsrFactories(),
    JsonDecoder::createWithAutodiscoveredPsrFactories()
);

$jsonData = $transport(
    new Request('GET', '/some/file', [], new FormDataPart([
        'name' => 'Jos bos',
        'profile-pic' => DataPart::fromPath('/my-profile-pic.jpg')
    ])),
);

If you wish not to use symfony/mime for this, you could use guzzle/psr7's MultipartStream with the existing StreamEncoder option:

[janvernieuwe]

Nice! this will make some (crappy) api's a lot easier to use!