minor #43612 [BrowserKit][HttpClient][Routing] support building query strings with stringables (nicolas-grekas, OskarStark)

This PR was merged into the 5.4 branch.

Discussion
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[BrowserKit][HttpClient][Routing] support building query strings with stringables

| Q             | A
| ------------- | ---
| Branch?       | 5.4
| Bug fix?      | no
| New feature?  | yes (minor)
| Deprecations? | no
| Tickets       | Fix #26992
| License       | MIT
| Doc PR        | -

Allows using eg an instance of `Uid` as a route parameter.

Replaces #42057

Commits
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65e2caca30 Add check and tests for public properties
ab38bb8b6c [BrowserKit][HttpClient][Routing] support building query strings with stringables

Author: Tobion

HttpBrowser.php

@@ -91,7 +91,18 @@ private function getBodyAndExtraHeaders(Request $request, array $headers): array
             return ['', []];
         }
 
-        return [http_build_query($fields, '', '&', \PHP_QUERY_RFC1738), ['Content-Type' => 'application/x-www-form-urlencoded']];
+        array_walk_recursive($fields, $caster = static function (&$v) use (&$caster) {
+            if (\is_object($v)) {
+                if ($vars = get_object_vars($v)) {
+                    array_walk_recursive($vars, $caster);
+                    $v = $vars;
+                } elseif (method_exists($v, '__toString')) {
+                    $v = (string) $v;
+                }
+            }
+        });
+
+        return [http_build_query($fields, '', '&'), ['Content-Type' => 'application/x-www-form-urlencoded']];
     }
 
     protected function getHeaders(Request $request): array