Refactor: migrate the function to specific file (#10201)

### What problem does this PR solve?

Move base64 related function to api/common/base64.py

### Type of change

- [x] Refactoring

---------

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

api/common/README.md

@@ -0,0 +1,2 @@
+The python files in this directory are shared between service. They contain common utilities, models, and functions that can be used across various
+services to ensure consistency and reduce code duplication.

api/common/base64.py

@@ -0,0 +1,21 @@
+#
+#  Copyright 2025 The InfiniFlow Authors. All Rights Reserved.
+#
+#  Licensed under the Apache License, Version 2.0 (the "License");
+#  you may not use this file except in compliance with the License.
+#  You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+#  Unless required by applicable law or agreed to in writing, software
+#  distributed under the License is distributed on an "AS IS" BASIS,
+#  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+#  See the License for the specific language governing permissions and
+#  limitations under the License.
+#
+
+import base64
+
+def encode_to_base64(input_string):
+    base64_encoded = base64.b64encode(input_string.encode('utf-8'))
+    return base64_encoded.decode('utf-8')

api/db/init_data.py

@@ -14,7 +14,6 @@
 #  limitations under the License.
 #
 import logging
-import base64
 import json
 import os
 import time
@@ -32,11 +31,7 @@ from api.db.services.llm_service import LLMService, LLMBundle, get_init_tenant_l
 from api.db.services.user_service import TenantService, UserTenantService
 from api import settings
 from api.utils.file_utils import get_project_base_directory
-
-
-def encode_to_base64(input_string):
-    base64_encoded = base64.b64encode(input_string.encode('utf-8'))
-    return base64_encoded.decode('utf-8')
+from api.common.base64 import encode_to_base64
 
 
 def init_superuser():