feat: DhcpConfig can now effectively manage a config file to add a static map entry

harmony-rs/opnsense-config-xml/src/xml_utils/mod.rs

@@ -1,6 +1,20 @@
-//mod generic_xml;
-//mod maybe_string;
-mod yaserde;
-//pub use generic_xml::*;
-//pub use maybe_string::*;
-pub use yaserde::*;
+use yaserde::YaSerialize;
+
+pub fn to_xml_str<T: YaSerialize>(model: &T) -> Result<String, String> {
+    let yaserde_cfg = yaserde::ser::Config {
+        perform_indent: true,
+        write_document_declaration: false,
+        pad_self_closing: false,
+        ..Default::default()
+    };
+    let serialized = yaserde::ser::to_string_with_config::<T>(model, &yaserde_cfg)?;
+
+    // Opnsense does not specify encoding in the document declaration
+    //
+    // yaserde / xml-rs does not allow disabling the encoding attribute in the
+    // document declaration
+    //
+    // So here we just manually prefix the xml document with the exact document declaration
+    // that opnsense uses
+    Ok(format!("<?xml version=\"1.0\"?>\n{serialized}\n"))
+}