private String logException(final Throwable throwable) {
    final StringWriter sw = new StringWriter();
    final PrintWriter pw = new PrintWriter(sw);
    throwable.printStackTrace(pw);
    pw.flush();
    return sw.toString();
  }
Create merge block creator for block header and fee recipient.

@param header the header
@param feeRecipient the fee recipient
@return the merge block creator
consensus/merge/src/main/java/org/hyperledger/besu/consensus/merge/blockcreation/MergeCoordinator.java