When it comes to storing people's funds, we must pay extra attention to how we do it since we could risk losing millions of dollars using our DAX. That's why the largest exchanges use cold storage with lots of security systems in place. Essentially, they keep funds offline in a remote location stored in secure hardware devices that are customized to their needs such as Trezor, Ledger, or their own.
In our case, we'll store funds in a series of smart contracts, known as escrows, whose only goal is to store people's money. There will be an escrow contract associated with each user account to independently secure all of their funds. That escrow contract will have a function to receive funds, only ERC20 tokens, and a function to extract funds executable by the owner of that escrow. Go ahead and create a folder...