Add a routing-focused test helper(s?) to assert on privileges

[jmileham]

Often, teams need to ensure that a whole set of related functionality is operating with a common security posture (e.g. admin-only). This related functionality is often mounted within a similar path. Being able to assert that a set of routes nested within a resource or namespace have either a certain minimum set of privileges or an exactly matching set of privileges seems very valuable to prevent accidental violations of expected authorization.

This could work based on path globbing, or routing tree nesting, or something like that. It'll take some R&D to find the sweet spot for developer experience that is intuitive to write and legible to readers of the resulting tests and failures.