Show Variant Option in Cart.

[krasej]

Currenty the lineItem Object contains in cart no information about the selected variant and no options object is available. The cart endpoint is fetched via GET so no options are passed.

Acceptance criteria:

• associations or includes params are extended with appropriate parameters to get the cart item's variant.
• helper is aligned with the new format needed

ux details: https://storybook.storefrontui.io/?path=/story/pages-cart--common