added alternative storage client instantiation method, corrected filepaths, added missing type hinting

backend/open_webui/config.py

@@ -590,6 +590,7 @@ S3_BUCKET_NAME = os.environ.get("S3_BUCKET_NAME", None)
 S3_ENDPOINT_URL = os.environ.get("S3_ENDPOINT_URL", None)
 
 GCS_BUCKET_NAME = os.environ.get("GCS_BUCKET_NAME", None)
+GCS_PROJECT_ID = os.environ.get("GCS_PROJECT_ID", None)
 GOOGLE_APPLICATION_CREDENTIALS_JSON = os.environ.get("GOOGLE_APPLICATION_CREDENTIALS_JSON", None)
 
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