quarkus: RESTEasy Reactive - mapping MULTIPART_FORM_DATA to request body don't work

Describe the bug

with https://github.com/quarkusio/quarkus/pull/27526 in place, my multiplart form data request body is always null. My endpoint looks like:

    // resource method
    @POST
    @Path("/echo")
    @Consumes(MediaType.MULTIPART_FORM_DATA)
    @Produces(MediaType.TEXT_PLAIN)
    public String echo(String requestBody) {
        return requestBody;
    }

same situation is for wrapper

    // resource method
    @POST
    @Consumes(MediaType.MULTIPART_FORM_DATA)
    @Produces(MediaType.TEXT_PLAIN)
    @Path("/upload-multipart")
    @Blocking
    public String uploadMultipart(FileWrapper body) {
        deathRow.add(body.file);
        return utils.getSum(body.file.getAbsoluteFile().toPath());
    }
...
    @RegisterForReflection
    public class FileWrapper {
        @RestForm("file")
        @PartType(MediaType.APPLICATION_OCTET_STREAM)
        public File file;
    
        @RestForm("name")
        @PartType(MediaType.TEXT_PLAIN)
        public String name;
    }

Expected behavior

• Provide a way how I can map the request to the String (ideally OOTB).
• Make docs dummy proof (customize docs for me).

Actual behavior

requestBody is always null. body is not null but its fields are null.

How to Reproduce?

Reproducer:

Steps to reproduce the behavior:

1. git clone https://github.com/quarkus-qe/quarkus-test-suite.git
2. cases

• cd quarkus-test-suite/http/jaxrs-reactive && mvn clean verify -Dit.test=MultipartClientIT
• cd quarkus-test-suite/http/rest-client-reactive && mvn clean verify -Dit.test=LargeFileHandlingIT#uploadMultipart

Output of uname -a or ver

No response

Output of java -version

No response

GraalVM version (if different from Java)

No response

Quarkus version or git rev

No response

Build tool (ie. output of mvnw --version or gradlew --version)

No response

Additional information

No response