Update RetCode to common.constants (#10984)

### What problem does this PR solve?

1. Update RetCode to common.constants
2. Decouple the admin and API modules

### Type of change

- [x] Refactoring

---------

Signed-off-by: Jin Hai <haijin.chn@gmail.com>

api/apps/file2document_app.py

@@ -24,9 +24,9 @@ from flask_login import login_required, current_user
 from api.db.services.knowledgebase_service import KnowledgebaseService
 from api.utils.api_utils import server_error_response, get_data_error_result, validate_request
 from common.misc_utils import get_uuid
+from common.contants import RetCode
 from api.db import FileType
 from api.db.services.document_service import DocumentService
-from api import settings
 from api.utils.api_utils import get_json_result
 
 
@@ -108,7 +108,7 @@ def rm():
     file_ids = req["file_ids"]
     if not file_ids:
         return get_json_result(
-            data=False, message='Lack of "Files ID"', code=settings.RetCode.ARGUMENT_ERROR)
+            data=False, message='Lack of "Files ID"', code=RetCode.ARGUMENT_ERROR)
     try:
         for file_id in file_ids:
             informs = File2DocumentService.get_by_file_id(file_id)