digest: parse without storing 'value' in local buffer

[bagder]

Use of curlx_str_ functions avoids having a copy.

[Copilot]

🟡 Changes recommended

lib/vauth/digest.h now references struct Curl_str without a forward declaration or include, which breaks compilation for translation units including this header.

Once you've addressed the issues Copilot identified, you can request another Copilot review.

Pull request overview

This PR updates Digest authentication challenge parsing to avoid copying directive names into a local buffer by switching to curlx_str_* parsing helpers and struct Curl_str views.

Changes:

• Change Curl_auth_digest_get_pair() to return the directive name via struct Curl_str instead of a fixed-size char[] buffer.
• Replace manual blank-skipping and string comparisons with curlx_str_passblanks() and curlx_str_casecompare().
• Add curlx/strparse.h include where needed for the new parsing helpers.

File summaries

File	Description
lib/vauth/digest.h	Updates Curl_auth_digest_get_pair() signature to use struct Curl_str *.
lib/vauth/digest.c	Refactors digest challenge parsing to use curlx_str_* helpers and Curl_str comparisons.
lib/vauth/digest_sspi.c	Refactors SSPI digest parsing similarly and adds curlx/strparse.h.

Review details

• Files reviewed: 3/3 changed files
• Comments generated: 1
• Review effort level: Lite

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[testclutch]

Analysis of PR #22831 at 9fcfa933:

Test ../../tests/http/test_19_shutdown.py::TestShutdown::test_19_03_shutdown_by_server[http/1.1] failed, which has NOT been flaky recently, so there could be a real issue in this PR. Note that this test has failed in 2 different CI jobs (the link just goes to one of them). Note that this CI job has had a number of other flaky tests recently (2, to be specific) so it may be that this failure is rather a systemic issue with this job and not with this specific PR.

Generated by Testclutch