No need for breaking backwards compatibility here - encapsulating the
logic for `getAttributes()` in one place turns out to be quite useful.
Refs #1931.
This gives extension authors time to add the new `getAttributes()`
method to their `BlueprintInterface` implementations.
The layer itself is easy to remove in beta.14.
Forces notifications into a dedicated SendNotificationsJob and passed
to the queue.
- One static method re-used in the job ::getAttributes, is that okay or
use a trait?
- Do we want to use this solution and refactor into a better Hub after
stable, postpone this implementation or use it in b11?
