TL;DR: This is a required update for all testnet nodes, and is highly recommended for mainnet nodes if you were using the deprecated getaddressesbyaccount RPC method.
Added v5 transactions to standard rules
In v4.5.0 we added the v5 transaction format to the NU5 consensus rules for testnet. However, it was omitted from the standard rules, which meant that zcashd testnet nodes would not accept v5 transactions into their mempools, causing them to not be propagated or mined. This release updates the zcashd standard rules to accept v5 transactions alongside v4 transactions.
New listaddresses RPC method
The listaddresses endpoint has been added to the RPC API. This method allows the caller to obtain addresses managed by the wallet, grouped by the source of the address, including both those addresses generated by the wallet and those associated with imported viewing or spending keys. This provides functionality that replaces and subsumes the previously removed getaddressesbyaccount method.
