fix: Content-Length Header Conflict When Using Transfer-Encoding: chunked

[klkucaj]

The HTTP specification (RFC 7230) states that when Transfer-Encoding: chunked is used, the Content-Length header must not be present in the same message. Including both headers causes ambiguity in how the body length is determined and violates the HTTP/1.1 standard.

Current Behavior:
When the Transfer-Encoding header includes chunked (alone or in combination with other encodings like gzip), the Content-Length header is still being sent in some cases. This results in undefined behavior and may cause protocol errors for HTTP clients or servers.

Expected Behavior:

• If Transfer-Encoding: chunked is present, the Content-Length header should be omitted.
• For other Transfer-Encoding values (e.g., gzip, compress, deflate) without chunked, the Content-Length can be included.

Examples of Valid Cases:
✅ Transfer-Encoding: chunked (no Content-Length)
✅ Transfer-Encoding: gzip + Content-Length: 100
✅ Transfer-Encoding: deflate + Content-Length: 256

Examples of Invalid Cases:
❌ Transfer-Encoding: chunked + Content-Length: 100
❌ Transfer-Encoding: gzip, chunked + Content-Length: 150

Steps to Reproduce:

1. Send an HTTP request or response with Transfer-Encoding: chunked and Content-Length set.
2. Observe that both headers are sent.

Impact:
This issue violates HTTP/1.1 specifications and can lead to inconsistent handling of the response body by clients or servers, causing errors or unexpected behaviors.

Proposed Fix:

• Add a validation step to ensure that if Transfer-Encoding contains chunked, the Content-Length header is not included.
• Log or throw an error if both headers are detected.