fix(router): preserve rewrite-phase query argument changes during servlet URI normalization

[Ankit-cs]

Description

Background & Problem:

When apisix.normalize_uri_like_servlet is enabled, $upstream_uri was materialized before route rewrite and access plugins executed.

Some plugins modify the request arguments dynamically during these later phases. For example, key-auth and jwt-auth remove query credentials via core.request.set_uri_args() when hide_credentials: true is configured. Because $upstream_uri already contained a snapshot of the earlier query string, those query modifications were not reflected in the URI forwarded upstream, causing credentials to leak and query argument changes to be lost.

Solution:

1. Store the normalized servlet path separately in api_ctx.servlet_upstream_uri instead of eagerly writing to api_ctx.var.upstream_uri.
2. Assemble $upstream_uri with the updated $is_args$args after the rewrite and access plugin phases have completed.
3. Respect plugin precedence: if a plugin like proxy-rewrite explicitly sets api_ctx.var.upstream_uri, do not overwrite it.
4. Updated proxy-mirror to also respect servlet_upstream_uri.
5. Added regression test cases in t/router/servlet-upstream-uri.t covering:
   • apisix.normalize_uri_like_servlet: true
   • query-based key-auth with hide_credentials: true
   • unrelated query arguments remaining intact
   • clean URI with no trailing ? when all arguments are stripped.

Which issue(s) this PR fixes:

Fixes #13983

Checklist

• I have explained the need for this PR and the problem it solves
• I have explained the changes or the new features added to this PR
• I have added tests corresponding to this change
• I have updated the documentation to reflect this change (Documentation unchanged: this is a bug fix restoring expected behavior)
• I have verified that this change is backward compatible

[Ankit-cs]

as i am learning lua for the first time so that is the reason i got late in solving the bug @Baoyuantop sir and looking for feedback also.

[Baoyuantop]

Early plugins lose servlet path parameters

With servlet normalization enabled, upstream_uri stays empty during rewrite and access plugins. The external pre-request runner sees a stripped path, and GraphQL introspection can target a different endpoint than the forwarded request.

Example: For /anything;jsessionid=x, the pre-request runner now receives /anything; the upstream receives /anything;jsessionid=x. A GraphQL endpoint available only at the latter path fails schema discovery at the former path.

[Ankit-cs]

OK @Baoyuantop i will solve this

[Ankit-cs]

Hi @Baoyuantop,looking for another feedback!

I've updated the PR so that api_ctx.var.upstream_uri is populated early with the safe-encoded servlet path (/anything;jsessionid=x), allowing early plugins like ext-plugin and graphql-limit-count to observe the servlet path parameters. The final query string ($is_args$args) is then synchronized after rewrite and access phases finish to preserve query modifications (e.g. hide_credentials).

I also added a regression test in t/router/servlet-upstream-uri.t covering this scenario.

[Ankit-cs]

Hi @Baoyuantop sir can you look a minute for my pr it will be really great if you provide some feedback