Resteasy reactive - Handling Generics in request body

[aravindtga]

Describe the bug

Generics arguments are not getting mapped properly from request and throwing the below exception

java.lang.ClassCastException: class java.util.HashMap cannot be cast to class org.generictype.Item 
        (java.util.HashMap is in module java.base of loader 'bootstrap'; org.generictype.Item is in unnamed module of loader 
        io.quarkus.bootstrap.classloading.QuarkusClassLoader @1e1e0d04)

Quarkus version: 1.13.3.Final
Zulip discussion: Discussion

To Reproduce

Reproducer link:
https://github.com/aravindtga/Quarkus-generic-request-body-jsonb

Steps to reproduce the behavior:

1. Run the provided application
2. Hit the endpoint "/endpoint" with the request body

{
    "content": {
        "name":"firstname",
        "email":"myemail"
    }
}

[quarkus-bot]

/cc @FroMage, @geoand, @stuartwdouglas