Transfer-Encoding header is set twice

[FloGro3]

Describe the bug

In our BFFs we found out that when receiving a response from the backend that has "Transfer-Encoding" header set to "chunked" and we forward this response to the FE suddenly there are two "Transfer-Encoding" headers present which are set to "chunked". The browser is ignoring this but some rest clients are throwing an error because of theses duplicate headers.

Expected behavior

"Transfer-Encoding" header is only present once in the response of the bff.

Actual behavior

"Transfer-Encoding" header is set twice.

How to Reproduce?

Here is a minimal project that reproduces the issue: https://github.com/FloGro3/response-header-issue-example

Output of uname -a or ver

No response

Output of java -version

Java version: 19.0.2

Quarkus version or git rev

3.12.3

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

Apache Maven 3.9.7

Additional information

No response

[quarkus-bot]

/cc @FroMage (resteasy-reactive), @stuartwdouglas (resteasy-reactive)