Message id from notification payload. Notification sent by trigger.

Hello, sorry, I haven't noticed your message until today. Here is the pull-request.

It's quite straightforward. The message id is taken from notification payload. Notification is sent by trigger on table update/insert. 

It fixes the issue of worker restart: messages without locked_at are noop updated which triggers the notifications again so the worker re-receives lost messages.

Cheers, M.