Rich Notifications

To implement rich notifications you will have to create a new Notification Service Target that will be responsible for downloading the media of the notification and attach it to the notification object.

In Xcode go to File -> New -> Target and choose Notification Service Extension

Keep in mind that notifications don't have much time to download the media attached, if the download doesn't finish in a short period of time the notification will be delivered without the media.

To handle MPush attachments add this your NotificationService should look like this:

override func didReceive(_ request: UNNotificationRequest, withContentHandler contentHandler: @escaping (UNNotificationContent) -> Void) {
    self.contentHandler = contentHandler
    bestAttemptContent = (request.content.mutableCopy() as? UNMutableNotificationContent)

    if let bestAttemptContent = bestAttemptContent {
        if let mediaUrl = request.content.userInfo["media_url"] as? String, let fileUrl = URL(string: mediaUrl) {
            downloadMedia(fileUrl: fileUrl, request: request, bestAttemptContent: bestAttemptContent) {
                contentHandler(bestAttemptContent)
            }
        } else {
            contentHandler(bestAttemptContent)
        }
    }
}

func downloadMedia(fileUrl: URL, request: UNNotificationRequest, bestAttemptContent: UNMutableNotificationContent, completion: @escaping () -> Void) {
    let task = URLSession.shared.downloadTask(with: fileUrl) { (location, _, _) in
        if let location = location {
            let tmpDirectory = NSTemporaryDirectory()
            let tmpFile = "file://".appending(tmpDirectory).appending(fileUrl.lastPathComponent)
            let tmpUrl = URL(string: tmpFile)!
            do {
                try FileManager.default.moveItem(at: location, to: tmpUrl)

                var options: [String: String]? = nil
                if let type = request.content.userInfo["media_type"] as? String {
                    options = [String: String]()
                    options?[UNNotificationAttachmentOptionsTypeHintKey] = type
                }
                if let attachment = try? UNNotificationAttachment(identifier: "media." + fileUrl.pathExtension, url: tmpUrl, options: options) {
                    bestAttemptContent.attachments = [attachment]
                }
                completion()
            } catch {
                completion()
            }
        }
    }
    task.resume()
}

override func serviceExtensionTimeWillExpire() {
    // Called just before the extension will be terminated by the system.
    // Use this as an opportunity to deliver your "best attempt" at modified content, otherwise the original push payload will be used.
    if let contentHandler = contentHandler, let bestAttemptContent =  bestAttemptContent {
        contentHandler(bestAttemptContent)
    }
}

With this code, we download the attachment, if exists, and move it to a temporary directory. Then we add it to our notification with

if let attachment = try? UNNotificationAttachment(identifier: "media." + fileUrl.pathExtension, url: tmpUrl, options: options) {
    bestAttemptContent.attachments = [attachment]
}