fix bug where '/' was not properly inserted in s3 key strings

backend/open_webui/storage/provider.py

@@ -94,7 +94,7 @@ class S3StorageProvider(StorageProvider):
             aws_secret_access_key=S3_SECRET_ACCESS_KEY,
         )
         self.bucket_name = S3_BUCKET_NAME
-        self.key_prefix = S3_KEY_PREFIX
+        self.key_prefix = S3_KEY_PREFIX if S3_KEY_PREFIX else "" 
 
     def upload_file(self, file: BinaryIO, filename: str) -> Tuple[bytes, str]:
         """Handles uploading of the file to S3 storage."""
@@ -150,7 +150,7 @@ class S3StorageProvider(StorageProvider):
 
     # The s3 key is the name assigned to an object. It excludes the bucket name, but includes the internal path and the file name.
     def _extract_s3_key(self, full_file_path: str) -> str:
-        return ''.join(full_file_path.split("//")[1].split("/")[1:])
+        return '/'.join(full_file_path.split("//")[1].split("/")[1:])
     
     def _get_local_file_path(self, s3_key: str) -> str:
         return f"{UPLOAD_DIR}/{s3_key.split('/')[-1]}"