private static function normalizeNestedFileSpec(array $files = []): array
    {
        $normalizedFiles = [];

        foreach (array_keys($files['tmp_name']) as $key) {
            $spec                  = [
                'tmp_name' => $files['tmp_name'][$key],
                'size'     => $files['size'][$key],
                'error'    => $files['error'][$key],
                'name'     => $files['name'][$key],
                'type'     => $files['type'][$key],
            ];
            $normalizedFiles[$key] = self::createUploadedFileFromSpec($spec);
        }

        return $normalizedFiles;
    }