What is the correct way to upload a file using the clientUploader plugin, and what common mistake should be avoided?

To upload a file, send a POST to `/service/extension/clientUploader/upload` with `Content-Type: multipart/form-data; boundary=...` and include a `Cookie: ZM_ADMIN_AUTH_TOKEN`. A common mistake is manually setting the `Content-Type` header with a fixed boundary; this causes the request library to regenerate a different boundary, breaking the upload. Instead, use the `requests_toolbelt` library's `MultipartEncoder` to ensure the boundary matches exactly. This upload capability is part of the expanded features described in Zimbra SOAP API Development Guide 2.