Add support for Lock-Token header in DavResponse

- Updated `DAV` header to include version 2.
- Introduced `setLockToken` method to add a `Lock-Token` header.

src/Bundle/ChillDocStoreBundle/Dav/Response/DavResponse.php

@@ -19,6 +19,13 @@ class DavResponse extends Response
     {
         parent::__construct($content, $status, $headers);
 
-        $this->headers->add(['DAV' => '1']);
+        $this->headers->add(['DAV' => '1,2']);
+    }
+
+    public function setLockToken(string $token): self
+    {
+        $this->headers->add(['Lock-Token' => $token]);
+
+        return $this;
     }
 }