Support managing snapshot policies

[swoehrl-mw]

Discussed in https://github.com/opensearch-project/opensearch-k8s-operator/discussions/796

The operator already supports managing snapshot repositories. A step further would be to add a custom resource and reconciler logic (similar to ISMPolicies) to also manage snapshot policies via the operator.

[prudhvigodithi]

[Triage] Thanks @swoehrl-mw so the idea is to have a CRD to configure a snapshot policy ? @bbarani

[swoehrl-mw]

@prudhvigodithi

so the idea is to have a CRD to configure a snapshot policy ?

Exactly. We can introduce a new CRD for that and add a reconciler to the operator to handle it.