Globally change the appearance of the application. Light/Dark mode and color.

    func scene(_ scene: UIScene, 
               willConnectTo session: UISceneSession,
               options connectionOptions: UIScene.ConnectionOptions) {
        self.window?.overrideUserInterfaceStyle = AppearanceService.shared.theme.getUserInterfaceStyle()
        self.window?.tintColor = AppearanceService.shared.color.getColorStyle()
    }

    func application(_ application: UIApplication, 
                     didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool {
        if UserDefaults.standard.object(forKey: DefaultKeys.switchState) == nil {
            UserDefaults.standard.set(true, forKey: DefaultKeys.switchState)
        }
        if UserDefaults.standard.object(forKey: DefaultKeys.selectedColor) == nil {
            UserDefaults.standard.set(5, forKey: DefaultKeys.selectedColor)
        }
        return true
    }