How can I use the API to post an additional charge on a customers account?
In one case, we don't know the shipping cost ahead of time. I'm thinking we charge $0 for shipping and use the authorize only setting for that account. We can then authorize the charge when the customer agrees to the additional shipping cost. After capturing the original charge, we still need to be able to charge the additional fee.
Would this have to be a completely separate transaction?
Also I read somewhere in the docs that the only way to create a transaction is with a cart. Does that mean I have to create a $0 cart with a shipping fee, then post it to the transactions endpoint to get my new shipping only transaction?
It'd be nice to have some examples of creating transactions, but I couldn't find any.