Adding "Networking requirements" section to the Preparing the installation documentation

[ibuziuk]

Is your task related to a problem? Please describe

by default, k8s / OpenShift has a flat network where pods from different namespaces can communicate with one another. However, if some NetworkPolicies are applied that could cause networking issues for Eclipse Che e.g. pods from user namespaces can not communicate with the pod in the namespace where the operator is installed. Need to document the NetworkPolicies on the clusters for k8s / OpenShift

Describe the solution you'd like

https://www.eclipse.org/che/docs/stable/administration-guide/preparing-the-installation/ should contain a section that describes requirments for Network Policies requirements

Describe alternatives you've considered

N/A

Additional context

No response

[tolusha]

If there are any restriction on the cluster, then we have explicitly allow traffic from openshift-devspaces namespace:

  - apiVersion: networking.k8s.io/v1
    kind: NetworkPolicy
    metadata:
      name: allow-from-openshift-devspaces
    spec:
      ingress:
        - from:
            - namespaceSelector:
                matchLabels:
                  kubernetes.io/metadata.name: openshift-devspaces
      podSelector: {}
      policyTypes:
        - Ingress

[ibuziuk]

@dkwon17 has added some details during the WTO onboarding - https://issues.redhat.com/projects/WTO/issues/WTO-142