[Feature] Simplify reconciliation by simplifying claim logic for StatefulSet, Service and ConfigMap based on Etcd resource name

[amshuman-kr]

Feature (What you would like to be added):

The reconciliation flow of etcd-druid includes claiming from potentially multiple pre-existing StatefulSet, Service and ConfigMap objects if they exist. This is done by selecting the objects based on spec.selector in the Etcd resource, claiming one of the matching objects (if any) and deleting the rest of the objects (if any). If no matching objects are found then a new object is created.

The logic of claiming from multiple pre-existing objects objects based onspec.selector was done because of the following reasons.

1. Migration from the time before etcd-druid was introduced. I.e. adopting objects created from the time before etcd-druid was introduced minimised and simplified clean up.
2. Keeping options open before multi-node ETCD design was finalised to use a single StatefulSet for all the members of an ETCD cluster. Another alternative of using one StatefulSet for each member of an ETCD cluster was still open at that time.

Now that the migration scenario as well as the multi-node design don't need the functionality of claiming from multiple pre-existing objects, we can simplify the claim logic to just pick the object to be claimed by the same name as the Etcd resource . We will still need the claim functionality to mark it as claimed, of course.

Motivation (Why is this needed?):

Approach/Hint to the implement solution (optional):

[timuthy]

/assign

[timuthy]

/unassign due to restricted capacity

[abdasgupta]

Closing this issue as we no longer follow claim logic