您需要按如下所述创建通知服务扩展

以下步骤对我很有效：
步骤1 -添加通知服务扩展
第2步-将目标添加到Podfile
步骤3 -使用扩展帮助程序
NotificationService.swift在Swift中：

//
//  NotificationService.swift
//  RichNotification
//

import UserNotifications

class NotificationService: UNNotificationServiceExtension {
    var contentHandler: ((UNNotificationContent) -> Void)?
    var bestAttemptContent: UNMutableNotificationContent?
    
    override func didReceive(_ request: UNNotificationRequest, withContentHandler contentHandler: @escaping (UNNotificationContent) -> Void) {
        self.contentHandler = contentHandler
        bestAttemptContent = (request.content.mutableCopy() as? UNMutableNotificationContent)
        
        guard let bestAttemptContent = bestAttemptContent,
              let attachmentURLAsString = bestAttemptContent.userInfo["image"] as? String,
              let attachmentURL = URL(string: attachmentURLAsString) else {
            return
        }
        
        downloadImageFrom(url: attachmentURL) { (attachment) in
            if let attachment = attachment {
                bestAttemptContent.attachments = [attachment]
                contentHandler(bestAttemptContent)
            }
        }
    }

    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)
        }
    }
    
    private func downloadImageFrom(url: URL, with completionHandler: @escaping (UNNotificationAttachment?) -> Void) {
        let task = URLSession.shared.downloadTask(with: url) { (downloadedUrl, response, error) in
            // 1. Test URL and escape if URL not OK
            guard let downloadedUrl = downloadedUrl else {
                completionHandler (nil)
                return
            }
            // 2. Get current's user temporary directory path
            var urlPath = URL(fileURLWithPath: NSTemporaryDirectory ())
            // 3. Add proper ending to url path, in the case jpg (The system validates the content of attached files before scheduling the corresponding notification request. If an attached file is corrupted,
            let uniqueURLEnding = ProcessInfo.processInfo.globallyUniqueString + ".jpg"
            urlPath = urlPath.appendingPathComponent (uniqueURLEnding)
            // 4. Move downloadedUrl to newly created urlPath
            try? FileManager.default.moveItem(at: downloadedUrl, to: urlPath)
            // 5. Try adding getting the attachment and pass it to the completion handler
            do {
                let attachment = try UNNotificationAttachment (identifier: "picture", url: urlPath, options: nil)
                completionHandler(attachment)
            }
            catch {
                completionHandler(nil)
            }
        }
        task.resume()
    }
}

extension UNNotificationRequest {
    var attachment: UNNotificationAttachment? {
        guard let attachmentURL = content.userInfo["image"] as? String, let imageData = try? Data(contentsOf: URL(string: attachmentURL)!) else {
            return nil
        }
        return try? UNNotificationAttachment(data: imageData, options: nil)
    }
}

extension UNNotificationAttachment {
    convenience init(data: Data, options: [NSObject: AnyObject]?) throws {
        let fileManager = FileManager.default
        let temporaryFolderName = ProcessInfo.processInfo.globallyUniqueString
        let temporaryFolderURL = URL(fileURLWithPath: NSTemporaryDirectory()).appendingPathComponent(temporaryFolderName, isDirectory: true)

        try fileManager.createDirectory(at: temporaryFolderURL, withIntermediateDirectories: true, attributes: nil)
        let imageFileIdentifier = UUID().uuidString + ".jpg"
        let fileURL = temporaryFolderURL.appendingPathComponent(imageFileIdentifier)
        try data.write(to: fileURL)
        try self.init(identifier: imageFileIdentifier, url: fileURL, options: options)
    }
}

通过Firebase/FCM发送推送通知的cURL

curl --location --request POST 'https://fcm.googleapis.com/fcm/send' \
--header 'Authorization: key=<YOUR FCM KEY>' \
--header 'Content-Type: application/json' \
--data-raw '{
    "to": "fcm token for device or channel id",
    "content_available": true,
    "mutable_content": true,
    "notification": {
        "title": "Notification With Image",
        "mutable-content": true,
        "body": "Test Message "
    }, 
    "data": {
        "image": "https://upload.wikimedia.org/wikipedia/commons/1/16/HDRI_Sample_Scene_Balls_%28JPEG-HDR%29.jpg"
    }
}'