Use ModelUtils.hasAnyOf/hasOneOf helpers per review

Per @jpfinne.

Author: winrid

modules/openapi-generator/src/main/java/org/openapitools/codegen/DefaultCodegen.java

@@ -2759,8 +2759,7 @@ protected void updateModelForComposedSchema(CodegenModel m, Schema schema, Map<S
 
         // For anyOf/oneOf, required fields should be the intersection across members,
         // not the union. A field is only guaranteed present if ALL members require it.
-        boolean isAnyOfOrOneOf = (composed.getAnyOf() != null && !composed.getAnyOf().isEmpty())
-                || (composed.getOneOf() != null && !composed.getOneOf().isEmpty());
+        boolean isAnyOfOrOneOf = ModelUtils.hasAnyOf(composed) || ModelUtils.hasOneOf(composed);
         List<Set<String>> perMemberRequiredSets = isAnyOfOrOneOf ? new ArrayList<>() : null;
 
         if (!interfaces.isEmpty()) {