Add notification dismissal swipe action

#49

Pachyderm/Model/Notification.swift

@@ -15,9 +15,9 @@ public class Notification: Decodable {
     public let account: Account
     public let status: Status?
     
-    public static func dismiss(_ notification: Notification) -> Request<Empty> {
+    public static func dismiss(id notificationID: String) -> Request<Empty> {
         return Request<Empty>(method: .post, path: "/api/v1/notifications/dismiss", body: .parameters([
-                "id" => notification.id
+                "id" => notificationID
             ]))
     }
     

Tusker/Screens/Notifications/NotificationsTableViewController.swift

@@ -140,7 +140,32 @@ class NotificationsTableViewController: EnhancedTableViewController {
     }
     
     override func tableView(_ tableView: UITableView, trailingSwipeActionsConfigurationForRowAt indexPath: IndexPath) -> UISwipeActionsConfiguration? {
-        return (tableView.cellForRow(at: indexPath) as? TableViewSwipeActionProvider)?.trailingSwipeActionsConfiguration()
+        let dismissAction = UIContextualAction(style: .destructive, title: NSLocalizedString("Dismiss", comment: "dismiss notification swipe action title")) { (action, view, completion) in
+            let group = DispatchGroup()
+            self.groups[indexPath.row].notificationIDs
+                .map(Pachyderm.Notification.dismiss(id:))
+                .forEach { (request) in
+                    group.enter()
+                    MastodonController.client.run(request) { (response) in
+                        group.leave()
+                    }
+            }
+            group.notify(queue: .main) {
+                self.groups.remove(at: indexPath.row)
+                self.tableView.deleteRows(at: [indexPath], with: .automatic)
+                completion(true)
+            }
+        }
+        dismissAction.image = UIImage(systemName: "clear.fill")
+        let cellConfiguration = (tableView.cellForRow(at: indexPath) as? TableViewSwipeActionProvider)?.trailingSwipeActionsConfiguration()
+        let config: UISwipeActionsConfiguration
+        if let cellConfiguration = cellConfiguration {
+            config = UISwipeActionsConfiguration(actions: [dismissAction] + cellConfiguration.actions)
+        } else {
+            config = UISwipeActionsConfiguration(actions: [dismissAction])
+        }
+        config.performsFirstActionWithFullSwipe = true
+        return config
     }
     
     @objc func refreshNotifications(_ sender: Any) {