Improves error message context for validation errors

Updates validation error messages to include the absolute path
of the error. This provides more context for debugging and
understanding where the validation failed, especially for
complex data structures. Also modifies error message for root
level errors.

Author: anlu85

core_directory/serializers.py

@@ -327,4 +327,4 @@ def _format_core_validation_error(self, e, file_type):
         key = '::'.join(e.absolute_path)
         default_message = {'default': e.message}
         error_message =  validator_error_messages.get(key, default_message).get(e.validator, e.message)
-        return f'Validation error in {file_type} file at {key or 'root'}: {error_message}'
+        return f'Validation error in {file_type} file at {key or "root"}: {error_message}'