Returns the maximum amount that can be spent with a single transaction on the wallet.
The maximum spendable amount can differ from a wallet’s total balance. A transaction can only use up to 200 unspents. Wallets that have more than 200 unspents cannot spend the full balance in one transaction. Additionally, the value returned for the maximum spendable amount accounts for the current fee level by deducting the estimated fees. The amount will only be calculated based on the unspents that fit the parameters passed.