Mobile-friendly UI for registration, account details updating, etc

[kjagiello]

Currently, customers need to contact one of the staff members in order to change any account details or in order to register the card. The idea is to present a QR-code in the kiosk UI, let the customer scan it and it will lead them to either registration page or a profile page, where account details can be updated, purchase history viewed, etc. Everything should be mobile friendly.

Prioritised task list:

• Registration page
• Account details page
• Purchase history

[kjagiello]

@ElinSwedin I've mentioned earlier that the data in the QR-code should be some kind of temporary authentication token that could be used by the user to access different endpoints, like this for example /user/<token>/ or /user/<token>/history/ etc. The token could be produced using cryptographic signing, so we would need to store anything in database. I've mentioned JSON Web Tokens, but there is also a cryptographic signing API provided in Django. Both seem perfectly fine for our us, but the Django one is already available to us, so no need for an additional dependency.