User registration

[irony]

Before applying to a DIS or creating a DIS the user needs to register.

Best right now is to implement some form of magic link to the users email so we don't have to handle passwords at all, or use Github login since we require GitHub anyway right now.

Look at Loopback auth for more info on how to implement passport and JWT.

Important note: It should always be possible to browse through both DIS:es and Tenders without logging in.