User impersonation

[groenroos]

Add a facility for the developer to impersonate an end user, and view the app as if they were the end user.

[groenroos]

Unclear what mechanism to activate and deactivate this would make sense - perhaps a default /api hook?

It was a feature in the legacy code AFAIR, but it seems like such an edge case feature that I might even be tempted to spin this out into a separate package.