Update a PSBT with input information from the wallet and then sign inputs that the wallet can sign for.
psbtstringREQUIREDsignbooleanoptionalsighashtypestringoptionalbip32derivsbooleanoptionalfinalizebooleanoptionalcurl --user myuser --data-binary '{"jsonrpc":"1.0","id":"1","method":"walletprocesspsbt","params":["psbt_base64"]}' -H 'content-type:text/plain;' http://127.0.0.1:8332/{
"psbt": "cHNidP8BAFUCAAAAAe...",
"complete": true
}