Adds a private key (as returned by dumpprivkey) to your wallet. Requires a new wallet backup. Only for legacy wallets.
privkeystringREQUIREDlabelstringoptionalrescanbooleanoptionalcurl --user myuser --data-binary '{"jsonrpc":"1.0","id":"1","method":"importprivkey","params":["privkey","label",false]}' -H 'content-type:text/plain;' http://127.0.0.1:8332/null