Starts the checkout process, identifying the customer, optionally the cashier and obtaining a session.
This is the entry point of each transaction. The identification of the customer can be done trough several methods, specifying IdentifierMethod, IdentifierCode (and thirdPartySystemId if it applies) Wapping.Checkout.Api.Models.Enum.IdentifierMethodTypes
The other important part is the OrderCode, it has to identify univocally the code of the order in the system. This is usually a code that the POS gives to each order, or the same with ecommerce.
*There are cases in wich the code is not generated until the order is done, in some ecommerce for example. In that case, a temporal unique identifier has to be specified, and confirmed with the final one in the Commit.