Feat/dataset service api (#1245)

Co-authored-by: jyong <jyong@dify.ai>
Co-authored-by: StyleZhang <jasonapring2015@outlook.com>

api/services/errors/__init__.py

@@ -1,7 +1,7 @@
 # -*- coding:utf-8 -*-
 __all__ = [
     'base', 'conversation', 'message', 'index', 'app_model_config', 'account', 'document', 'dataset',
-    'app', 'completion', 'audio'
+    'app', 'completion', 'audio', 'file'
 ]
 
 from . import *

api/services/errors/file.py

@@ -3,3 +3,11 @@ from services.errors.base import BaseServiceError
 
 class FileNotExistsError(BaseServiceError):
     pass
+
+
+class FileTooLargeError(BaseServiceError):
+    description = "{message}"
+
+
+class UnsupportedFileTypeError(BaseServiceError):
+    pass