chore: add message status enum (#21825)

Co-authored-by: 刘江波 <jiangbo721@163.com>

api/core/app/task_pipeline/based_generate_task_pipeline.py

@@ -19,7 +19,7 @@ from core.app.entities.task_entities import (
 from core.errors.error import QuotaExceededError
 from core.model_runtime.errors.invoke import InvokeAuthorizationError, InvokeError
 from core.moderation.output_moderation import ModerationRule, OutputModeration
-from models.model import Message
+from models.model import Message, MessageStatus
 
 logger = logging.getLogger(__name__)
 
@@ -62,7 +62,7 @@ class BasedGenerateTaskPipeline:
             return err
 
         err_desc = self._error_to_desc(err)
-        message.status = "error"
+        message.status = MessageStatus.ERROR
         message.error = err_desc
         return err