route.meta.auth should be deprecated and renamed to something more meaningful

[dschmidt]

This is a follow up ticket for #7072.

meta.auth is used in isUserContext. If it's false, we don't necessarily need a user context - it could be a public link context as well.
The name doesn't reflect what it's actually good for. We need a better name and a sane default.

First ideas included userContextRequired: false, hybridContext: true, …