feat: [backend] vision support (#1510)

Co-authored-by: Garfield Dai <dai.hai@foxmail.com>

api/controllers/service_api/app/message.py

@@ -12,7 +12,7 @@ from libs.helper import TimestampField, uuid_value
 from services.message_service import MessageService
 from extensions.ext_database import db
 from models.model import Message, EndUser
-
+from fields.conversation_fields import message_file_fields
 
 class MessageListApi(AppApiResource):
     feedback_fields = {
@@ -43,6 +43,7 @@ class MessageListApi(AppApiResource):
         'inputs': fields.Raw,
         'query': fields.String,
         'answer': fields.String,
+        'message_files': fields.List(fields.Nested(message_file_fields), attribute='files'),
         'feedback': fields.Nested(feedback_fields, attribute='user_feedback', allow_null=True),
         'retriever_resources': fields.List(fields.Nested(retriever_resource_fields)),
         'created_at': TimestampField