Admin home + user details API

[jb3]

Once users login, we need to send them somewhere. We should create an admin homepage that any user token can access which will then direct users to areas they have permissions to access.

In order to render this page, we'll need a backend endpoint that can return details on the current user (most of the user model, realistically) and fetch this on the frontend after login.

We should support pagination and rudimentary search (email, username) on the backend.