Endpoint will return
null if spot margin is not enabled in account settings.
|borrowed||number||Amount of coin currently borrowed|
|free||number||Amount of coin that can be spent buying the other coin in the supplied market, including what's borrowable with margin|
|estimatedRate||number||Estimated hourly borrow rate for the next spot margin cycle|
|previousRate||number||Hourly borrow rate in the previous spot margin cycle|