Background download from app extension in SwiftyDropbox

Turns out I've been building against an old version (6.0.3); I'll upgrade to 8.2.1 and get back to you!

For what it's worth, the download code is fairly basic at this point:

        logger.log("dbx_downloadWithProgress: Downloading" + filePath)

        let destination: (URL, HTTPURLResponse) -> URL = { temporaryURL, response in

            return destURL

        }

            self.client?.files.download(path: filePath, overwrite: true, destination: destination)

                .response { response, error in

                    if let (responseMetadata, responseURL) = response {

                        completionHandler(responseURL, nil)

                    } else if let error = error {

                        print(error)        // TBD: error handling!

                        self.logger.log("dbx_downloadConfig ERROR: \(error)")

                        completionHandler(nil, error)       // TBD: need to map the passed-in error to a file-provider one

                    }

                }

                .progress { progressData in

                    // TBD:  need to pass in and implement progress display callback

                    self.logger.log("dbx_downloadConfig PROGRESS: \(progressData)")

                    print(progressData)

            }