Duplicate Transfer-Encoding: chunked headers in Quarkus response

[suchwerk]

Describe the bug

When making a (big) post request to a Quarkus endpoint, the response contains duplicate Transfer-Encoding: chunked headers. This is not valid per the HTTP specification and can cause issues with clients or proxies that strictly validate responses. In my case it clashes with caddy proxy (caddy is using a very strict go lib). I saw this in Quarkus Version 3.26.2 and 3.23.4

Expected behavior

The response should include the Transfer-Encoding: chunked header only once.

Actual behavior

HTTP/1.1 200 OK
Transfer-Encoding: chunked
Content-Type: application/json
Transfer-Encoding: chunked

How to Reproduce?

https://github.com/suchwerk/quarkus-duplicate-transfer-encoding

Just run the test to reproduce.

[quarkus-bot]

/cc @FroMage (rest)

[geoand]

Thanks for the reproducer!

#49894 fixes the issue