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

[membphis]

Background

#13982 fixes query-string loss when apisix.normalize_uri_like_servlet is enabled by appending the current $is_args$args value to $upstream_uri.

Problem

$upstream_uri is materialized before route rewrite and access plugins run. Some plugins modify the live request arguments later. For example, key-auth and jwt-auth remove a query credential through ngx.req.set_uri_args() when hide_credentials is enabled.

Because $upstream_uri already contains a copy of the earlier query string, those later argument changes are not reflected in the URI sent upstream.

Example:

Incoming request: /echo?auth=secret&foo=1
Early upstream_uri: /echo?auth=secret&foo=1
Arguments after key-auth: foo=1
URI sent upstream: /echo?auth=secret&foo=1
Expected upstream URI: /echo?foo=1

The same ordering can affect other plugins that modify request arguments after servlet URI normalization.

Expected behavior

Servlet-style path normalization should preserve the path parameters while the final upstream URI observes query argument changes made by rewrite or access plugins. A plugin that explicitly sets $upstream_uri should continue to take precedence.

Suggested direction

Keep the servlet path separately, then serialize the current $is_args$args value after the relevant plugin phases have completed. Do not overwrite an $upstream_uri explicitly set by a plugin.

Add a regression test covering:

• apisix.normalize_uri_like_servlet: true
• query-based key-auth or jwt-auth
• hide_credentials: true
• an unrelated query argument that must still reach the upstream

Related

• fix(router): keep the query string when normalize_uri_like_servlet is on #13982