Add skeleton UserActivityService.

Riot/Managers/Activities/UserActivityService.swift

@@ -0,0 +1,50 @@
+// 
+// Copyright 2021 New Vector Ltd
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+
+import Foundation
+import MatrixSDK
+
+@objcMembers
+class UserActivityService: NSObject {
+
+    // MARK: - Constants
+
+    // TODO: Move constants in here from UserActivities.m
+
+    // MARK: - Properties
+
+    #warning("This is initialised lazily so currently only observes left rooms if RoomViewController has been presented.")
+    static let shared = UserActivityService()
+
+    // MARK: - Setup
+
+    private override init() {
+        super.init()
+
+        NotificationCenter.default.addObserver(self, selector: #selector(didLeaveRoom(_:)), name: .mxSessionDidLeaveRoom, object: nil)
+    }
+
+    // MARK: - Public
+
+    func update(_ activity: NSUserActivity, from room: MXRoom) {
+        // TODO: Convert objc code into here.
+    }
+
+    func didLeaveRoom(_ notification: Notification) {
+        guard let roomId = notification.userInfo?[kMXSessionNotificationRoomIdKey] as? String else { return }
+        // TODO: Remove the room from spotlight
+    }
+}

Riot/Modules/Room/RoomViewController.m

@@ -2007,6 +2007,9 @@ - (void)becomeCurrentActivity
         self.userActivity = [[NSUserActivity alloc] initWithActivityType:kUserActivityTypeMatrixRoom];
     }
 
+    // TODO: Move everything else into the method called below
+    [UserActivityService.shared update:self.userActivity from:self.roomDataSource.room];
+
     self.userActivity.title = self.roomDataSource.room.summary.displayname;
     self.userActivity.requiredUserInfoKeys = [[NSSet alloc] initWithObjects:kUserActivityInfoRoomId, nil];