fun Double?.toUsdString(maxDecimals: Int = USD_FORMATTER.maximumFractionDigits, minDecimals: Int = USD_FORMATTER.minimumFractionDigits): String
Format a USD value into USD with the given number of digits, represented as a string. Start with USD -> end with USD.
maxDecimals - the number of decimal places to use in the format. Default is 6 because
ZEC is glorious.
minDecimals - the minimum number of digits to allow to the right of the decimal.
Return
this Double ZEC value represented as a string with at least minDecimals and at most
maxDecimals, which is 2 by default. Zero is always represented without any decimals.