Fix required attribute not being respected in XSD generation

- Modified XsdGenerator to respect field.isRequired() directly instead of depending on enforceMandatoryElements parameter
- Removed required=true from type field in modello.mdo since type is optional when association is present
- Required fields now correctly omit minOccurs="0" in generated XSD, making them mandatory

Co-authored-by: slachiewicz <[email protected]>

Author: Copilot

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

@@ -232,9 +232,7 @@ private void writeComplexTypeDescriptor(
                     }
                     w.startElement("xs:element");
 
-                    if (!enforceMandatoryElements || !field.isRequired()) {
-                        // Usually, would only do this if the field is not "required", but due to inheritance, it may be
-                        // present, even if not here, so we need to let it slide
+                    if (!field.isRequired()) {
                         w.addAttribute("minOccurs", "0");
                     }
                 }

src/main/mdo/modello.mdo

@@ -672,7 +672,6 @@
         <field xml.insertParentFieldsUpTo="versionRange">
           <name>type</name>
           <version>1.0.0+</version>
-          <required>true</required>
           <type>String</type>
           <description><![CDATA[
             Simple type for this field (or array of such type). Can be one of : <code>boolean</code>, <code>byte</code>,