fix: use locale-agnostic uppercase in metamodel generator (#700)

The metamodel generator was using String.toUpperCase() without specifying
a locale, causing non-ASCII characters in generated field names when
running in Turkish locale. For example, 'id' was converted to 'İD'
instead of 'ID'.

Changed all toUpperCase() calls to use Locale.ROOT for consistent ASCII
uppercase conversion regardless of system locale settings:
- MetamodelGenerator: Map field values and nested field names
- ObjectUtils.staticField(): Static field name generation

Author: bsbodden

redis-om-spring/src/main/java/com/redis/om/spring/metamodel/MetamodelGenerator.java

@@ -490,7 +490,7 @@ else if (Map.class.isAssignableFrom(targetCls)) {
             // Generate the special VALUES field for querying map values
             if (valuesInterceptor != null) {
               String mapFieldName = field.getSimpleName().toString();
-              String mapValuesFieldName = mapFieldName.toUpperCase().replace("_", "") + "_VALUES";
+              String mapValuesFieldName = mapFieldName.toUpperCase(Locale.ROOT).replace("_", "") + "_VALUES";
 
               // Add the VALUES field as a special metamodel field
               Triple<ObjectGraphFieldSpec, FieldSpec, CodeBlock> valuesField = generateMapValuesFieldMetamodel(entity,
@@ -514,8 +514,8 @@ else if (Map.class.isAssignableFrom(targetCls)) {
                   if (subfieldElement.getAnnotation(com.redis.om.spring.annotations.Indexed.class) != null) {
                     String subfieldName = subfieldElement.getSimpleName().toString();
                     String jsonFieldName = getJsonFieldName(subfieldElement);
-                    String nestedFieldName = field.getSimpleName().toString().toUpperCase().replace("_",
-                        "") + "_" + subfieldName.toUpperCase().replace("_", "");
+                    String nestedFieldName = field.getSimpleName().toString().toUpperCase(Locale.ROOT).replace("_",
+                        "") + "_" + subfieldName.toUpperCase(Locale.ROOT).replace("_", "");
 
                     TypeMirror subfieldTypeMirror = subfieldElement.asType();
                     String subfieldTypeName = subfieldTypeMirror.toString();

redis-om-spring/src/main/java/com/redis/om/spring/util/ObjectUtils.java

@@ -873,7 +873,7 @@ public static String replaceIfIllegalJavaIdentifierCharacter(final String word)
    */
   public static String staticField(final String externalName) {
     requireNonNull(externalName);
-    return ObjectUtils.toUnderscoreSeparated(javaNameFromExternal(externalName)).toUpperCase();
+    return ObjectUtils.toUnderscoreSeparated(javaNameFromExternal(externalName)).toUpperCase(java.util.Locale.ROOT);
   }
 
   /**