on signet
  "default_witness_commitment" : "hex"     (string, optional) a valid witness commitment for the unmodified block template
}

Examples:
> bitcoin-cli getblocktemplate '{"rules": ["segwit"]}'
> curl --user myusername --data-binary '{"jsonrpc": "1.0", "id": "curltest", "method": "getblocktemplate", "params": [{"rules": ["segwit"]}]}' -H 'content-type: text/plain;' http://127.0.0.1:8332/


