[gabor-lbl]

Adding the following endpoints for persistent services:

GET /persistent-service/servers
GET /persistent-service/servers/{server}/clusters
GET /persistent-service/servers/{server}/clusters/{cluster}/projects
POST /persistent-service/servers/{server}/clusters/{cluster}/namespaces
POST /persistent-service/servers/{server}/kubeconfig

This is based on our use-case of a multi-tenant k8s server that organizes users into project. If a facility doesn't have projects, they're not required.

• server: this is an actual k8s server
• cluster: an environment on the server (eg. prod, dev, etc.)
• project: a rancher concept to support multi-tenancy (optional)
• create namespace: this call is special because it takes a project (if supported) - so we can't just call the k8s api here
• create a kubeconfig: create a config file, which can then be used to make k8s api calls