xml: Add namespace prefixes

crates/xml/src/lib.rs

@@ -98,4 +98,5 @@ impl XmlDeserialize for Unparsed {
 pub trait XmlRootTag {
     fn root_tag() -> &'static [u8];
     fn root_ns() -> Option<Namespace<'static>>;
+    fn root_ns_prefixes() -> HashMap<Namespace<'static>, &'static [u8]>;
 }

crates/xml/src/se.rs

@@ -50,7 +50,7 @@ impl<T: XmlSerialize + XmlRootTag> XmlSerializeRoot for T {
         &self,
         writer: &mut quick_xml::Writer<W>,
     ) -> std::io::Result<()> {
-        let namespaces = HashMap::new();
+        let namespaces = Self::root_ns_prefixes();
         self.serialize(Self::root_ns(), Some(Self::root_tag()), &namespaces, writer)
     }
 }