NewCustomer is a factory to create a new Customer aggregate It will validate that the name is not empty.

NewProduct will create a new product will return error if name of description is empty.

ErrInvalidPerson is returned when the person is not valid in the NewCustome factory.

ErrMissingValues is returned when a product is created without a name or description.

Customer is an aggregate that combines all entities needed to represent a customer.

Product is a aggregate that combines item with a price and quantity.