chore: introduce phpstan level 6 (#7269)

Author: VincentLanglet

Controller/ApiPlatformController.php

@@ -103,7 +103,7 @@ private function getUriVariables(Request $request, HttpOperation $operation): ar
     {
         $uriVariables = [];
         foreach ($operation->getUriVariables() ?? [] as $parameterName => $_) {
-            $parameter = $request->route($parameterName);
+            $parameter = $request->route((string) $parameterName);
             if (\is_string($parameter) && ($format = $request->attributes->get('_format')) && str_contains($parameter, $format)) {
                 $parameter = substr($parameter, 0, \strlen($parameter) - (\strlen($format) + 1));
             }

Exception/ErrorHandler.php

@@ -77,7 +77,7 @@ public function render($request, \Throwable $exception)
             $operation = null;
             foreach ($resourceCollection as $resource) {
                 foreach ($resource->getOperations() as $op) {
-                    foreach ($op->getOutputFormats() as $key => $value) {
+                    foreach ($op->getOutputFormats() ?? [] as $key => $value) {
                         if ($key === $format) {
                             $operation = $op;
                             break 3;