Migrate function-based views into class-based views

[andreibosco]

Check:

• https://docs.djangoproject.com/en/3.0/topics/class-based-views/
• https://ccbv.co.uk/
• https://medium.com/@ksarthak4ever/django-class-based-views-vs-function-based-view-e74b47b2e41b
• https://simpleisbetterthancomplex.com/series/2017/10/09/a-complete-beginners-guide-to-django-part-6.html
• https://tests4geeks.com/blog/class-based-views-django-tutorial/
• https://simpleisbetterthancomplex.com/article/2017/03/21/class-based-views-vs-function-based-views.html