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

Author: nicolas-grekas

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