restrict manager resource cache based on namespaces from environment

[leelavg]

always cache resources from operator deployed namespace and provider an option to user for caching resources from other namespaces via WATCH_NAMESPACE env var with a comma separated namespace values.

fixes: #184

[leelavg]

tested, peak usage was 50 Mi for startup down from ~ 1.5 Gi on a semi-prod cluster.

[Madhu-1]

The namespace(s) name needs to be configurable as this operator is developed to work with multiple namespaces

https://sdk.operatorframework.io/docs/building-operators/golang/operator-scope/#configuring-watch-namespaces-dynamically is the way we need to look to fix this one.

[leelavg]

Yes, I want to refactor when we actually need it and so reused operator namespace.

[Madhu-1]

Yes, I want to refactor when we actually need it and so reused operator namespace.

IMO, it should be implemented in the above-requested manner instead of immediately changing it and later refactoring it. @nb-ohad WDYT?

[leelavg]

The namespace(s) name needs to be configurable as this operator is developed to work with multiple namespaces

https://sdk.operatorframework.io/docs/building-operators/golang/operator-scope/#configuring-watch-namespaces-dynamically is the way we need to look to fix this one.

• multi namespace is not working, need to go through controller-runtime code on what changed.

[leelavg]

done.

[leelavg]

/assign @nb-ohad @Madhu-1