Start or resume a multi-part upload or copy of a file. By default this method is idempotent, so subsequent calls will simply return the current status of the file upload/copy.
The body of the request will determine if an upload or a copy is performed: Using a MultipartUploadRequest will start a normal multipart upload, while posting a MultipartUploadCopyRequest will start a multipart copy.
|Optional parameter. When 'forceRestart=true' is included, any upload state for the given file will be cleared and a new upload will be started.|