Marketplace Checkout with Swaps

[BellringerQuinn]

Now that we have #193 and #244, let's combine the two. As an example, if a user wants to purchase an ERC1155 priced in USDC, but they only have WMATIC. The SDK should fetch a quote for them to buy the ERC1155s in WMATIC (by getting a SwapPrice for the required amount of USDC) and, if accepted, the SDK should batch the swap and purchase transactions together and execute them.