Full class at https://github.com/alexstyl/Memento-Calendar/blob/develop/android_mobile/src/main/java/com/alexstyl/specialdates/dailyreminder/AndroidDailyReminderNotifier.kt

notifyContacts.kt

    private fun notifyContacts(viewModels: List<ContactEventNotificationViewModel>) {
        viewModels.forEach { viewModel ->
            val requestCode = NotificationConstants.CHANNEL_ID_CONTACTS.hashCode() + viewModel.hashCode()
            val startIntent = PersonActivity.buildIntentFor(context, viewModel.contact)
            val pendingIntent = PendingIntent.getActivity(
                    context,
                    requestCode,
                    startIntent,
                    PendingIntent.FLAG_UPDATE_CURRENT)


            val notification =
                    NotificationCompat.Builder(context, NotificationConstants.CHANNEL_ID_CONTACTS)
                            .setContentTitle(viewModel.title)
                            .setContentText(viewModel.label)
                            .setContentIntent(pendingIntent)
                            .setSmallIcon(R.drawable.ic_stat_memento)
                            .setColor(colors.getDailyReminderColor())
                            .setGroup(NotificationConstants.DAILY_REMINDER_GROUP_ID)
                            .setGroupAlertBehavior(NotificationCompat.GROUP_ALERT_SUMMARY)
                            .setAutoCancel(true)
                            .addActionsFrom(viewModel)
                            .loadLargeImage(viewModel.contact.imagePath)
                            .build()
            notificationManager.notify(viewModel.notificationId, notification)
        }
    }