Validate route requirements

Problem/Motivation

While working on the routing YAML to attribute conversions, it struck me that there is no validation for the requirements array.

For example if you make a typo in _csrf_token then your route is not protected, when you might assume that it is.

Steps to reproduce

Proposed resolution

Figure out if it is possible to validate route requirements; given that requirement can be dynamic then this may be hard or require new APIs.

Remaining tasks

User interface changes

Introduced terminology

API changes

Data model changes

Release notes snippet