Implement authentication

[SoptikHa2]

• Implement using standard asp.net core methods
• Preferably as middleware?
• Roles: no auth, contestant, organizer
• Add example usage

[MistrMxyzptlk]

Added basic model it will be in pull request into dev, please look at it and say what should be changed before I will start implementin the rest.

Btw there will be needed an Email provider, are we able to get one? Or should we just dich Email Confirmation?