fix: skip Accept-Encoding during header passthrough (#2214)

[Caisin]

背景

开启请求头透传后，使用 curl 请求可能报错：
invalid character '\x1f' looking for beginning of value（bad_response_body）。

根因

透传规则（* / re:）把客户端 Accept-Encoding 也转发到了上游。
在这种情况下，上游可能返回 gzip 压缩响应体，而当前链路会把该二进制内容按 JSON 解析，导致首字节 0x1f 触发解析失败。

修复内容

• 在请求头透传黑名单中新增 accept-encoding，避免通过通配/正则透传该头。
• 新增测试 TestProcessHeaderOverride_PassthroughSkipsAcceptEncoding，验证透传时会跳过 Accept-Encoding。

验证

• go test ./relay/channel -run TestProcessHeaderOverride -count=1
• go test ./relay/channel -count=1

影响范围

• 仅影响“按名称透传”的头部规则（* / re: / regex:）。
• 不影响其他头透传逻辑。
• 显式 header override 仍可按配置覆盖。

Summary by CodeRabbit

• Bug Fixes
  • Resolved incorrect header forwarding behavior in API requests to properly exclude accept-encoding headers while maintaining request traceability.

[coderabbitai]

Walkthrough

Added "accept-encoding" to the passthrough skip header set in the API request handler to prevent this header from being forwarded by passthrough rules. A corresponding test validates that the Accept-Encoding header is properly omitted while preserving other headers like X-Trace-Id.

Changes

Cohort / File(s)	Summary
Header Skip Configuration relay/channel/api_request.go	Extended passthroughSkipHeaderNamesLower to include "accept-encoding", preventing this header from being forwarded in passthrough header rules.
Validation Test relay/channel/api_request_test.go	Added TestProcessHeaderOverride_PassthroughSkipsAcceptEncoding to verify that Accept-Encoding is omitted when passthrough headers are configured, while preserving X-Trace-Id.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~8 minutes

Poem

🐰 A header's been skipped from the flow,
Accept-Encoding won't steal the show,
Clean passthrough rules, no escape in sight,
With tests in place, everything's right!
hop hop ✨

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title accurately describes the main change: adding Accept-Encoding to the header passthrough skip list to fix JSON parsing errors.
Linked Issues check	✅ Passed	The pull request directly addresses issue #2214 by preventing gzip-compressed responses from being misinterpreted as JSON through header passthrough blacklisting.
Out of Scope Changes check	✅ Passed	All changes are scoped to fixing the Accept-Encoding header passthrough issue: modifications to skip header set and corresponding test coverage.
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.

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✨ Finishing Touches

• 📝 Generate docstrings (stacked PR)
• 📝 Generate docstrings (commit on current branch)

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Post copyable unit tests in a comment

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[seefs001]

有你说的issues之前还没请求头透传功能呢。。。
可以看你遇到的情况来调整，但是没必要挑着以前的issues来猜测吧

[Caisin]

我用了请求头透传，出现了这个问题

{"error":{"message":"invalid character '\x1f' looking for beginning of value","type":"bad_response_body","param":"","code":"bad_response_body"}}
然后修复了后
搜索看到了这个issue,顺手关闭下

[seefs001]

我用了请求头透传，出现了这个问题

{"error":{"message":"invalid character '\x1f' looking for beginning of value","type":"bad_response_body","param":"","code":"bad_response_body"}} 然后修复了后 搜索看到了这个issue,顺手关闭下

是你自己遇到的那可以，这个Issue关联我就去掉了，他和这个毫无关系。