MM-61947 Run DND expiry job more often and round expiry time to match interval (#29938)

* MM-61947 Run DND expiry job more often and round expiry time to match interval

* Move comment to make it godoc-compatible

* Change truncateDNDEndTime to work with seconds

---------

Co-authored-by: Mattermost Build <build@mattermost.com>

server/channels/app/server.go

@@ -1782,14 +1782,14 @@ func cancelTask(mut *sync.Mutex, taskPointer **model.ScheduledTask) {
 func runDNDStatusExpireJob(a *App) {
 	if a.IsLeader() {
 		withMut(&a.ch.dndTaskMut, func() {
-			a.ch.dndTask = model.CreateRecurringTaskFromNextIntervalTime("Unset DND Statuses", a.UpdateDNDStatusOfUsers, 5*time.Minute)
+			a.ch.dndTask = model.CreateRecurringTaskFromNextIntervalTime("Unset DND Statuses", a.UpdateDNDStatusOfUsers, model.DNDExpiryInterval)
 		})
 	}
 	a.ch.srv.AddClusterLeaderChangedListener(func() {
 		mlog.Info("Cluster leader changed. Determining if unset DNS status task should be running", mlog.Bool("isLeader", a.IsLeader()))
 		if a.IsLeader() {
 			withMut(&a.ch.dndTaskMut, func() {
-				a.ch.dndTask = model.CreateRecurringTaskFromNextIntervalTime("Unset DND Statuses", a.UpdateDNDStatusOfUsers, 5*time.Minute)
+				a.ch.dndTask = model.CreateRecurringTaskFromNextIntervalTime("Unset DND Statuses", a.UpdateDNDStatusOfUsers, model.DNDExpiryInterval)
 			})
 		} else {
 			cancelTask(&a.ch.dndTaskMut, &a.ch.dndTask)