So I want a user to be able to transfer bundle items to another account if the user and the account they're transferring to both agree. I tried doing this with the OpenTrade and AcceptTrade calls but when I tried to mark the bundles as tradable it told me I couldn't do so.
I know I could do this with server calls by revoking items from user 1 and then rewarding them to user 2, but I want to be secure about this and not have the secret key available to the client.
In the specific scenario I want to do this, I'd be transferring a user 1's entire inventory, or at least all the bundle items to user 2.