S3: S3 Object Retention API to include XML namespace support (#7517)

* Refactor S3 Object Retention API to include XML namespace support and improve compatibility with Veeam. Updated XML tags to remove hardcoded namespaces and added test cases for retention and legal hold configurations without namespaces.

* Added XMLNS field setting in both places

weed/s3api/s3_constants/header.go

@@ -23,6 +23,11 @@ import (
 	"github.com/gorilla/mux"
 )
 
+// S3 XML namespace
+const (
+	S3Namespace = "http://s3.amazonaws.com/doc/2006-03-01/"
+)
+
 // Standard S3 HTTP request constants
 const (
 	// S3 storage class