Prevent enum item names being reserved keywords (OpenAPITools#17804)

Author: martonmiklos

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

@@ -928,10 +928,14 @@ public String toEnumVarName(String value, String datatype) {
 
         String var = value.replaceAll("\\W+", "_").toUpperCase(Locale.ROOT);
         if (var.matches("\\d.*")) {
-            return "_" + var;
-        } else {
-            return var;
+            var = "_" + var;
+        }
+
+        if (reservedWords.contains(var)) {
+            return escapeReservedWord(var);
         }
+
+        return var;
     }
 
     public boolean specVersionGreaterThanOrEqualTo310(OpenAPI openAPI) {