Allow namespace-scoped deployment

[juv]

Hi,

thanks for this project. In a multi tenant Kubernetes cluster, setting up new ClusterRole and ClusterRoleBinding resources is typically problematic and needs more consideration from the cluster administrator team. It would be great if kuma-ingress-watcher could be configured to either a) track Kubernetes resources in just a single namespace -- the one it is deployed in -- or b) to track the resources in a configurable list of namespaces. Most likely b) is the better approach as it is more flexible but of course also a bit more work. This allows the application to be deployed for single/multiple namespaces with just Role and RoleBinding resources.

As far as I understand from the Python code, the code is using the networking_api_instance.list_ingress_for_all_namespaces() to find all Ingress resources in the cluster is doing so similarly for IngressRoutes. I assume this portion of the code could be adjusted to somehow switch between a namespaced deployment mode and cluster-wide deployment mode.

Besides of that, there will also be a Helm Chart change necessary to not create the Cluster* resources in case of a namespaced deployment: ClusterRole and ClusterRoleBinding. If you want, I can help with that part. Unfortunately I am not a Python programmer so I would rather not get into implementing this feature itself in your Python code.

What do you think? :)