Commerce defines and populates two slots for messages:
/atg/commerce/pricing/CleanBeforePricingSlot: This slot contains stacking rule exclusion messages, for example, “The Free Scarf with all orders over $200 promotion cannot be applied as the limit on the number of promotions of this type has been reached.” This slot is emptied and repopulated with appropriate messages during each pricing operation./atg/commerce/pricing/NoCleanBeforePricingSlot: This slot contains gift with purchase messages, for example, “Congratulations! You qualify for a free gift.” UnlikeCleanBeforePricingSlot, messages in this slot are not removed until they are retrieved by the application. This means that this slot can contain messages from multiple pricing operations and those messages can be duplicates of each other or conflict with each other.
