private FailoverContext[] decodeContexts(ByteBuffer byteBuffer) {
        byteBuffer.slice();
        byte[] data = new byte[byteBuffer.remaining()];
        byteBuffer.get(data);
        return JsonUtils.decode(new String(data, StandardCharsets.UTF_8), FailoverContext[].class);
    }
Get the failover contexts from the given metadata delta.
It returns empty if there is no update for the failover key.
core/src/main/java/kafka/automq/failover/FailoverListener.java