AmountTotalMetadataKey is the metadata key for the total amount of the checkout same goes for this as well, it's always an interface{} of float64 type.

max: 999999.

ProcessedMetadataKey is the metadata key to indicate that the checkout has been processed in the system.

ProductQuantityMetadataKey is the metadata key for the quantity of the product it's necessary to cast as this properly because while storing metadata, it's serialized as json and when retrieved, it's always an interface{} of float64 type.