public void handlePrepareMessage(final Prepare msg) {
    LOG.debug(
        "Received a prepare message. round={}. author={}",
        roundState.getRoundIdentifier(),
        msg.getAuthor());
    peerIsPrepared(msg);
  }
Handle prepare message.

@param msg the msg
consensus/qbft-core/src/main/java/org/hyperledger/besu/consensus/qbft/core/statemachine/QbftRound.java