Before this change, Authorize() method was just returning an error,
regardless of whether the user is unauthorized or whether there
is some other unrelated error. Returning boolean with information
about user authorization and error (which should be unrelated to
the authorization) separately will make it easier to debug.
Fixes#27974
Added function to read basic ACL from a CSV file.
Added implementation of Authorize based on that file's policies.
Added docs on authentication and authorization.
Added example file and tested it.
Added basic interface for authorizer implementations.
Added default "authorize everything" and "authorize nothing
implementations.
Added authorization check immediately after authentication check.
Added an integration test of authorization at the HTTP level of
abstraction.
