add the pack model
add the mixed pack model
add the discount model
add the cart item model
add the tally model
add the cart model
add the interpretable module
add the discountable interpreter
add the taggable interpreter
add the money interpreter
add the percentage interpreter
add the product interpreter
add the savings interpreter
add the packable interpreter
add the mixed pack interpreter
add the discount interpreter
add the cart item interpreter
add the tally interpreter
add the totals interpreter
add the tag builder