[fopina-ci]

This is a PR-as-issue because Issues are disabled on this fork.

Reference implementation PR:
#1

TODO:

• after PR Support multi-value request headers #1 is reviewed/ready, clean this placeholder branch/file
• prepare the implementation cleanly for upstream
• push/open the real upstream PR against https://github.com/Danny-Dasilva/CycleTLS

The placeholder file exists only to keep this tracking PR open.

[fopina]

Working on gotlsproxy issue Danny-Dasilva#7:
fopina/gotlsproxy#7

Goal:
Improve CycleTLS header forwarding behavior in gotlsproxy.

Issue Danny-Dasilva#7 asks for two related fixes:

1. Support multiple values for request headers
   Current gotlsproxy code flattens req.Header into map[string]string for cycletls.Options.Headers.
   That drops all but the first value for headers with multiple values.

2. Preserve request header name casing
   CycleTLS internally uses Header.Set(k, v), which canonicalizes header names.
   Some servers are sensitive to header casing even though HTTP says they should not be.

Important dependency context:
CycleTLS project:
https://github.com/Danny-Dasilva/CycleTLS

Relevant CycleTLS issues / PRs:

• Open issue for duplicated headers:
  If header name is duplicated, the headers will be lost in nodejs  Danny-Dasilva/CycleTLS#251
  “If header name is duplicated, the headers will be lost in nodejs”
  Open, labeled help wanted and Selected for Development.

• Closed issue for header canonicalization:
  Add a way to not canonicalize headers Danny-Dasilva/CycleTLS#278
  “Add a way to not canonicalize headers”
  Closed as not_planned on 2024-06-17.

• Related open issue for non-string header values:
  Support non-string values in header object Danny-Dasilva/CycleTLS#338
  Not exactly duplicate headers, but related to expanding the header value model.

• Open CycleTLS v3 beta PR:
  Beta 3.0.0 release Danny-Dasilva/CycleTLS#415
  Mentions headers can have multiple values, but appears focused on response headers, not request header input or casing preservation.

Conclusion:
A gotlsproxy-only fix can join repeated request header values, but cannot fully preserve header casing because CycleTLS canonicalizes internally. Cleanest full fix is in CycleTLS: add support for multi-value request headers and assign directly into fhttp.Header instead of using Header.Set.