I am not a developer so forgive me if this is a stupid question. From what I understand it could be very expensive to store a large amount of data on the blockchain. For example, an auction site will need photos etc. Is there a mechanism for storing the bulk of the data "offchain" with only the bare minimum "onchain"? I understand that OpenBazaar uses the Bitcoin blockchain but that chain is only capable of storing units of value so how does that work for a fully functioning auction site? Maybe I have misunderstood how OpenBazaar works - is it on a private blockchain that simply uses Bitcoin as a payment mechanism?