import BackgroundTasks

struct PingApp: App {
    init() {
        ...
        BGTaskScheduler.shared.register(forTaskWithIdentifier: BackgroundTasks.cleanDBIdentifier, using: nil) { task in
            BackgroundTasks.shared.cleanDB()
            BackgroundTasks.shared.scheduleBackgroundTask()
            task.setTaskCompleted(success: true)
        }
    }
}

struct BackgroundTasks {
    public func cleanDB() {
        ...
        let oneWeekAgo = Calendar.current.date(byAdding: .day, value: -7, to: currentDate)!
        try threadContext.delete(model: ServerResponse.self, where: #Predicate { $0.date < oneWeekAgo })
        ...
    }
}