TEST: Added test cases for Upload Documents HTTP API (#5991)

### What problem does this PR solve?

cover upload docments endpoints

### Type of change

- [x] add test cases

sdk/python/test/libs/utils/__init__.py

@@ -0,0 +1,25 @@
+#
+#  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
+from pathlib import Path
+
+
+def encode_avatar(image_path):
+    with Path.open(image_path, "rb") as file:
+        binary_data = file.read()
+    base64_encoded = base64.b64encode(binary_data).decode("utf-8")
+    return base64_encoded