scrub database dump: implement private fields for classes (1/3)

[odo-sfct]

Part 1 | Part 2 | Part 3

Implements the first part of creating a scrub database dump script is to allow models to declare which fields are sensitive and scrubbed.

Models that have this should extend the interface by inheriting the mixin class and overriding the privacy_protected_method method. The types are mapped to Faker fake function implementations.