Let's assume we have 50 ERC20 tokens that we would like to support (deposits) on our website. People are depositing tokens to the ETH adresses we've generated for them.
In the end of the day, we want to geather tokens from all the generated addresses and send it to our cold wallet.
How can we make the transfer to the cold wallet if the newly generated addresses don't have any ether on it (this means no gas) and we don't want send there any ether?
Preferably, I would like to pay all the GAS that's requried for transactions from the cold wallet address - is it possible?
How exchanges are managing such situations? Do they generate the adresses and every time they are sending there eth to have enought for gas? In the end of the day, they have to move assests to one account. That's sounds... unefficent.