[MM-28985] Remove pointers to slice (part 1) (#18034)

* Remove pointers to slice (part 1)

* Remove use of pointers to slice from model package (#18045)

* Fix after merge

manualtesting/manual_testing.go

@@ -184,11 +184,11 @@ func getChannelID(a app.AppIface, channelname string, teamid string, userid stri
 		return "", false
 	}
 
-	for _, channel := range *channels {
+	for _, channel := range channels {
 		if channel.Name == channelname {
 			return channel.Id, true
 		}
 	}
-	mlog.Debug("Could not find channel", mlog.String("Channel name", channelname), mlog.Int("Possibilities searched", len(*channels)))
+	mlog.Debug("Could not find channel", mlog.String("Channel name", channelname), mlog.Int("Possibilities searched", len(channels)))
 	return "", false
 }