Endpoints to get current session and to logout

Exposed an endpoint to retrieve some information from the user session if it exists and another to log the current user out.

Done as a part of https://github.com/my-koop/service.website/issues/272
Copied from https://github.com/my-koop/module.user/blob/rc/lib/controllers/login.ts#L40

I've seen it used interchangeably, we're better not to?