Update channels in the background thread

import android.support.annotation.RequiresApi

import com.fsck.k9.Account

import com.fsck.k9.Preferences

import java.util.concurrent.Executors

class NotificationChannelUtils(private val context: Context, private val preferences: Preferences) {

            return

        }

        Executors.newSingleThreadExecutor().execute {

            val notificationManager = context.getSystemService(Context.NOTIFICATION_SERVICE)

                    as NotificationManager

            val accounts = preferences.accounts

            removeChannelsForNonExistingOrChangedAccounts(notificationManager, accounts)

            addChannelsForAccounts(notificationManager, accounts)

        }

    }