Check the timestamp of the last message before sending notifications

[kafeman]

Some users send many chat messages at once and we want to reduce the number of notifications.

Right now, there is a cron script running every 10 minutes which does this. But if the execution time of the script happens exactly in the in the middle of this bunch of messages, the user gets two notifications instead of one.

Instead, the script should check first if the last message was sent, say, more than 5 minutes ago. If it isn't, the sender is probably still spamming the poor recipient :-)