Uploads a file to the specified directory. If the file already exists (matching on the name), it will be overwritten. Otherwise a new file will be created. In either case, the file ID, whether created or updated, will be returned.
The ID of the directory into which the file should be uploaded. Use 0 to upload to the root
The name of the uploaded file
The binary file contents encoded as a base64 string
<?xml version="1.0" encoding="utf-8"?>
<![CDATA[ SUCCESS ]]>