kubernetes: cluster quorum status

## Summary

For node readiness check required simple test that cluster quorum exist.

## Desired Behaviour

Say request
```sh
curl http://127.0.0.1:5984/_membership
```
Will return response that have `quorum_present` string. Then this node may be used to service clients request. And kubernetes route client request to this node.

## Possible Solution
I not have

## Additional context

Kubernetes database and client pods starts in random order. Need to be sure that quorum exist before client will connected to CouchDB cluster.

The issue identifies the CouchDB _membership endpoint and Kubernetes node readiness as the entry points; start by checking how the response exposes quorum_present and how readiness is currently determined. Done means a node is reported ready only when quorum_present confirms that cluster quorum exists, with coverage for the readiness behavior.

Written by the indexing model from the issue text.