Connecting NiFi to ZooKeeper

NiFi in cluster mode requires a ZooKeeper ensemble for state management and leader election purposes, this operator at the moment does not support single node deployments without ZooKeeper, hence this is a required setting.

Configuration happens via a ConfigMap, which needs to contain two keys called ZOOKEEPER_HOSTS with the value being the ZooKeeper connection string and ZOOKEEPER_CHROOT with the value being the ZooKeeper chroot. This ConfigMap typically is created by a ZookeeperZnode of the ZooKeeper Operator.