Add K8up viewer and editor roles to default built-in roles

[ccremer]

Summary

As described in https://kubernetes.io/docs/reference/access-authn-authz/rbac/#aggregated-clusterroles, those will be added automatically, so that any "viewer" or "editor" can view/edit K8up resources also.

Closes #284

Checklist

• Keep pull requests small so they can be easily reviewed.
• Categorize the PR by setting a good title and adding one of the labels:
  bug, enhancement, documentation, change, breaking,
  as they show up in the changelog
• Link this PR to related issues.

[ccremer]

This creates a bunch of clusterroles:

$ k get clusterrole | grep k8up
k8up-archive-editor-role                                               2m3s
k8up-archive-viewer-role                                               2m3s
k8up-backup-editor-role                                                2m3s
k8up-backup-viewer-role                                                2m3s
k8up-check-editor-role                                                 2m3s
k8up-check-viewer-role                                                 2m3s
k8up-manager-role                                                      15m
k8up-prebackuppod-editor-role                                          2m3s
k8up-prebackuppod-viewer-role                                          2m3s
k8up-prune-editor-role                                                 2m3s
k8up-prune-viewer-role                                                 2m3s
k8up-restore-editor-role                                               2m3s
k8up-restore-viewer-role                                               2m3s
k8up-schedule-editor-role                                              2m3s
k8up-schedule-viewer-role                                              2m3s
k8up-snapshot-editor-role                                              2m3s
k8up-snapshot-viewer-role                                              2m3s

I'm starting to think that a consolidated viewer and editor role makes more sense than having individual cluster roles.

[cimnine]

I'm not quite certain I've fully understood the aggregated roles, so I can say little to that other than lgtm.

[ccremer]

I'm not quite certain I've fully understood the aggregated roles, so I can say little to that other than lgtm.

It basically means that any user can view or edit K8up resources without having to create explicit rolebindings for that. Provided they have the built-in-kubernetes-default view or edit roles resp.