Function apply_path_rewrite 

pub fn apply_path_rewrite(
    route: &Route,
    table: &RouteTable,
    idx: usize,
    path: &str,
    params: &[(String, String)],
) -> Option<String>

Apply a proxy action’s path rewrite (DW-010). params are the {param} captures of the exact-template match for this request (empty for regex/prefix routes); they are available to regex substitutions as $name references that miss the pattern’s own capture groups. Returns the rewritten path; a rewrite that does not apply (e.g. strip_prefix on a path that does not start with the prefix) leaves the path unchanged. The query string is NOT touched here — the caller re-attaches it. Public for the router golden-file tests.