Report subscription status

[ryannedolan]

Added logic to the subscription reconciler to keep track of deployed resources and to periodically check on their readiness. Subscription readiness is now predicated on the readiness of all resources in the pipeline.

Testing

Subscription status now progresses through multiple states:

$ kubectl get subscriptions -w
NAME       STATUS      DB         SQL
products               RAWKAFKA   SELECT "quantity", "product_id" AS KEY FROM INVENTORY."products_on_hand"
products   Planned.    RAWKAFKA   SELECT "quantity", "product_id" AS KEY FROM INVENTORY."products_on_hand"
products   Deployed.   RAWKAFKA   SELECT "quantity", "product_id" AS KEY FROM INVENTORY."products_on_hand"
products   Ready.      RAWKAFKA   SELECT "quantity", "product_id" AS KEY FROM INVENTORY."products_on_hand"

While the pipeline is being deployed, the operator periodically checks on the status of all resources:

Checking status of pipeline for Subscription/products...
Resource default/KafkaTopic/products-kafka-topic considered ready by default.
KafkaTopic/products-kafka-topic is ready.
FlinkDeployment/products-flink-job is NOT ready.
Pipeline for Subscription/products is NOT ready.
...
FlinkDeployment/products-flink-job is ready.
Subscription/products is ready.