All production classes are located in src/, and all unit and integration
tests are located in tests/.
This class bootstraps the phpList core system.
These classes are the domain models, which map to some of the database tables, and where the model-related business logic can be found. There must be no database access code in these classes.
These classes are reponsible for reading domain models from the database, for writing them there, and for other database queries.
These classes deal with security-related concerns, e.g., password hashing.