Introduce an AppMediator which will:

- combine multiple services to handle app wide requests
- remove direct UIApplication access from everywhere
- fix #2703 by combining UIApplication.applicationState with the WindowManager's main window appearance
- leave the door open for more app control in the future (especiall for the mac)

ElementX/Sources/Application/AppMediator.swift

@@ -0,0 +1,68 @@
+//
+// Copyright 2024 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 UIKit
+
+class AppMediator: AppMediatorProtocol {
+    private let windowManager: WindowManagerProtocol
+        
+    // UIApplication.State won't update if we store this e.g. in the constructor
+    private var application: UIApplication {
+        UIApplication.shared
+    }
+    
+    init(windowManager: WindowManagerProtocol) {
+        self.windowManager = windowManager
+    }
+    
+    func beginBackgroundTask(withName taskName: String?, expirationHandler handler: (() -> Void)?) -> UIBackgroundTaskIdentifier {
+        application.beginBackgroundTask(withName: taskName, expirationHandler: handler)
+    }
+
+    func endBackgroundTask(_ identifier: UIBackgroundTaskIdentifier) {
+        application.endBackgroundTask(identifier)
+    }
+    
+    func open(_ url: URL) {
+        application.open(url, options: [:], completionHandler: nil)
+    }
+    
+    func openAppSettings() {
+        guard let url = URL(string: UIApplication.openSettingsURLString) else {
+            return
+        }
+        
+        open(url)
+    }
+
+    var backgroundTimeRemaining: TimeInterval {
+        application.backgroundTimeRemaining
+    }
+
+    @MainActor
+    var appState: UIApplication.State {
+        switch application.applicationState {
+        case .active:
+            windowManager.mainWindow.traitCollection.activeAppearance == .active ? .active : .inactive
+        case .inactive:
+            .inactive
+        case .background:
+            .background
+        default:
+            .inactive
+        }
+    }
+}