[FEAT] Support envVars to define multiple C* and/or multiple Redis clusters.

[prasus]

Greetings,

I have created a helm chart which helps to deploy nf-data-explorer in Kubernetes clusters, while this works well, there is a limitation that we can only add a single C* and/or Redis cluster as environment variables, A workaround is to have one nf-data-explorer deployment per C* and redis clusters, which is not optimal 🙁

There is an option to use local file containing the list of clusters, but the discovery format requires ip, host details of the cluster members, which doesn't work well for clusters deployed in Kubernetes.

It would be really nice if we can either support envVars for specifying multiple clusters or have the discovery format in a Kubernetes friendly manner which accepts the k8s svc end points of the Cassandra and Redis clusters, Thanks!

Cheers,
Prasad.