We add the flake8 configuration used so we ensure everyone uses the same.
We remove the usage of __all__ for non public API.
When possible, we rationalize the class name according to its __name__ and module.
issue9082
review297061002
Retrieve dynamically the cost price methods to avoid other modules that extend
the cost price method field to also extend the configuration field.
issue5720
review25521002
Sergi Almacellas Abellana