fix: fix data type for message attribute

Author: UmaxCode

src/main/java/org/umaxcode/exception/ErrorMessage.java

@@ -10,6 +10,6 @@
 public class ErrorMessage {
 
     private String path;
-    private Object message;
+    private String message;
     private String timestamp;
 }

src/main/java/org/umaxcode/exception/GlobalExceptionHandler.java

@@ -62,7 +62,7 @@ public ErrorMessage handleArgumentNotValidException(MethodArgumentNotValidExcept
 
         return ErrorMessage.builder()
                 .path(request.getRequestURI())
-                .message(errors)
+                .message(errors.toString())
                 .timestamp(LocalDateTime.now().toString())
                 .build();
     }