feat(php-nextgen-client): add support for streaming (#19192)

Signed-off-by: Emilien Escalle <emilien.escalle@escemi.com>

samples/client/echo_api/php-nextgen/src/ObjectSerializer.php

@@ -452,6 +452,10 @@ class ObjectSerializer
             }
         }
 
+        if ($class === '\Psr\Http\Message\StreamInterface') {
+            return Utils::streamFor($data);
+        }
+
         if ($class === '\SplFileObject') {
             $data = Utils::streamFor($data);