Add comment explaining backward compatibility for enforceMandatoryElements parameter

Co-authored-by: slachiewicz <6705942+slachiewicz@users.noreply.github.com>

Author: Copilot

modello-plugins/modello-plugin-xsd/src/main/java/org/codehaus/modello/plugin/xsd/XsdGenerator.java

@@ -87,6 +87,8 @@ private void generateXsd(Map<String, Object> parameters) throws IOException, Mod
 
         // we assume parameters not null
         String xsdFileName = (String) parameters.get(ModelloParameterConstants.OUTPUT_XSD_FILE_NAME);
+        // enforceMandatoryElements parameter is kept for backward compatibility but is no longer used.
+        // Required fields are now always enforced based on field.isRequired() value.
         boolean enforceMandatoryElements =
                 Boolean.parseBoolean((String) parameters.get(ModelloParameterConstants.XSD_ENFORCE_MANDATORY_ELEMENTS));