Keep DDTraceStamp (#2960)

* Keep DDTraceStamp

While we no longer make use of it, immediately removing it may break existing applications. Let's keep it for a few versions and drop it later.

* Update src/DDTrace/Integrations/SymfonyMessenger/DDTraceStamp.php

Co-authored-by: Alexandre Choura <[email protected]>

---------

Co-authored-by: Alexandre Choura <[email protected]>

Author: bwoebi

src/DDTrace/Integrations/SymfonyMessenger/DDTraceStamp.php

@@ -0,0 +1,23 @@
+<?php
+
+namespace DDTrace\Integrations\SymfonyMessenger;
+
+use Symfony\Component\Messenger\Stamp\StampInterface;
+
+/**
+ * @deprecated since 1.5.0
+ */
+final class DDTraceStamp implements StampInterface
+{
+    private $headers;
+
+    public function __construct(array $headers)
+    {
+        $this->headers = $headers;
+    }
+
+    public function getHeaders(): array
+    {
+        return $this->headers;
+    }
+}