Retrieve a BIP 157 content filter for a particular block.
blockhashstringREQUIREDfiltertypestringoptionalcurl --user myuser --data-binary '{"jsonrpc":"1.0","id":"1","method":"getblockfilter","params":["00000000c937983704a73af28acdec37b049d214adbda81d7e2a3dd146f6ed09"]}' -H 'content-type:text/plain;' http://127.0.0.1:8332/{
"filter": "0163cb10fc8b...",
"header": "2b5adc66021d5c775.."
}