The progress of uploading the payload to the server for the upload request.
open var uploadProgress: Progress
Sets a closure to be called periodically during the lifecycle of the
UploadRequestas data is sent to the server.
After the data is sent to the server, the
progress(queue:closure:)APIs can be used to monitor the progress of data being read from the server.
open func uploadProgress(queue: DispatchQueue = DispatchQueue.main, closure: @escaping ProgressHandler) -> Self