refactor: Improve Forwarded header field parsing

[lmaisons]

Improve the Forwarded header field parsing in forwardedFor():

• Compute the correct remaining length using pointer arithmetic consistent with the rest of the function
• Add a directive-boundary predicate so for= is only matched at the start of the value or after a field delimiter per RFC 7239

[xrplf-ai-reviewer]

No issues.

Review by Claude Opus 4.6 · Prompt: V15

[codecov]

Codecov Report

❌ Patch coverage is 89.47368% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 82.1%. Comparing base (aa55392) to head (e11cc5d).
⚠️ Report is 12 commits behind head on develop.

Files with missing lines	Patch %	Lines
src/xrpld/rpc/detail/Role.cpp	89.5%	2 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##           develop   #7126   +/-   ##
=======================================
  Coverage     82.1%   82.1%           
=======================================
  Files         1010    1010           
  Lines        76064   76070    +6     
  Branches      7375    7370    -5     
=======================================
+ Hits         62470   62481   +11     
+ Misses       13594   13589    -5     

Files with missing lines	Coverage Δ
src/xrpld/rpc/detail/Role.cpp	91.4% <89.5%> (-0.4%)	⬇️

... and 3 files with indirect coverage changes

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[xrplf-ai-reviewer]

No issues.

Review by Claude Opus 4.6 · Prompt: V15

[xrplf-ai-reviewer]

No issues.

Review by Claude Opus 4.6 · Prompt: V15

[xrplf-ai-reviewer]

No issues.

Review by Claude Opus 4.6 · Prompt: V15

[pratikmankawde]

We can add tokenizing per RFC 7239 grammar instead of patching the std::search loop:

• Split on , boundaries (forwarded-element list)
• Trim white-spaces
• Split each element on ; (parameter list)
• Match directive name case-insensitively

The current approach (search + boundary-check + retry loop) works for the known cases, but it's fragile — any future directive containing the substring "for=" would require another boundary fix. A proper tokenizer eliminates this class of bugs entirely and is only marginally more code. Why do the same fix twice across two branches without addressing the structural weakness?

[a1q123456]

reapproving

[godexsoft]

I'd recommend to address @pratikmankawde comment in a follow up PR 👍

[bthomee]

@lmaisons is this ready to merge?