Tests for UserViewSet API enpoint, in particular /users/me
Tests for UserViewSet API enpoint, in particular /users/me

* A logged in user gets their own details at /users/me
* A non-logged in user gets a 400 bad request
* Admins can retrieve any user
* Regular users can only retrieve themselves.

ThreeDRadio/playlists,ThreeDRadio/playlists,ThreeDRadio/playlists