Bug 1030996 - Add in tool notifications

This is a draft for feedback
Thanks. That makes sense. I guess I was planning ahead just a bit, imagining that `check_notification` could get bigger as we have other reasons that notifications might occur. The middleware simply says that `check_notification` needs to get called, and then the results of that dealt with, so it might not have to change.

But considering that I haven't really put much thought into future-proofing the feature, I might as well just put it all into the middleware.