~~In-app notifications~~ Toasts

We use in-app notifications in a number of core apps and they address a fairly common design need. However, at present they are currently only provided by libgd.

Additionally, we've historically had a number of issues with the current in-app notification implementation. Sometimes people put too much content in them, so they look bad. Sometimes you end up with multiple notifications being shown at the same time.

We have designs for a new implementation which aims to eliminate these issues. The basic idea is that in-app notifications should behave much like regular notifications: you can set a string and set a button, but the app developer doesn't have control over the internal layout of the notification. Nor should they ideally have to worry about when each notification is shown, or showing them individually - that should be taken care of for them.