The [Navigation Lifecycle]
(https://vaadin.com/docs/v14/flow/routing/tutorial-routing-lifecycle.html) in the Vaadin 14 manual says:
It is also possible to register a standalone listener for this event using the
addBeforeEnterListener(BeforeEnterListener)method inUI.
But in modern Vaadin with the routing feature, we are no longer supposed to be writing a UI subsclass. My rough understanding is that there is indeed a UI object automatically instantiated for us, and then routing automatically replaces the content within that UI object. So the existence of a UI object is supposed to be transparent to us programmers using Vaadin Flow.
➥ So what is the lifecycle hook on a new UI instance so I can write a user-authentication check as a BeforeEnterListener to work globally across all my @Route views?
Calling [UI.getCurrent]
(https://vaadin.com/api/platform/14.0.0/com/vaadin/flow/component/UI.html#getCurrent--) will not do, as I would need to call that from somewhere in my layouts, but I am trying to register a listener before my layouts exist.
