fix(enums): add character handling for euro symbol (OpenAPITools#22414)

relates to OpenAPITools#22413

Author: rubenhoenle

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

@@ -1843,6 +1843,7 @@ public DefaultCodegen() {
     protected void initializeSpecialCharacterMapping() {
         // Initialize special characters
         specialCharReplacements.put("$", "Dollar");
+        specialCharReplacements.put("€", "Euro");
         specialCharReplacements.put("^", "Caret");
         specialCharReplacements.put("|", "Pipe");
         specialCharReplacements.put("=", "Equal");