[Catalyst] How to "sudo" using the Authentication plugin

[Robert Rothenberg]

We're working on an application with a lot of users, and where the passwords
are encrypted (and future versions may also allow OpenID logins).

Developers would like the ability for the "root" user to be able to become
another user, for the purposes of debugging problems that real users might
be having on a live system.

How does one do this using the Authentication plugin?

Obvious things to try like the $c->user($new_user) doesn't work, not does
the (internal) $c->set_authenticated($user, $real) method.