[helm] Add support for namespaced scope

[jkroepke]

Description

Classical service providers may not grant you admin permissions on our own kubernetes cluster. This changes introduce a namespaced modes, where external-dns runs namespace scoped.

Fixes #ISSUE

Checklist

• Unit tests updated
• End user documentation updated

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i though about create a dedicated role.yaml file first, but then I was the disadvantage of maintain to roles inside the helm chart.

[stevehipwell]

This approach makes sense given the constraints. I'll review properly on a big screen in the morning.

[stevehipwell]

This looks good, but I have a couple of questions.

[jkroepke]

I add a section about namespace scoped installation. All sources that depends against namespace scoped resources are working in namespaced scoped installation. Istio is a bit tricky here, because depends against 2 namespace scoped resources, but it would only work if both are in the same namespace.

I started with an quick table/support matrix, but I stop it. Most of the CRDs are namespaced scope, like RouteGroups, Openshift Routes, VirtualServices, getambassador/ingress...

I guess the RBAC for nodes can be still gated, since the Node permissions are only needed, if the annotation external-dns.alpha.kubernetes.io/endpoints-type: NodeExternalIP is defined.

I only test ingress objects, for the sources, I looked into the source code. Based on that, i have no idea, why contour-httpproxy need node permissions.

[stevehipwell]

/ok-to-test

[stevehipwell]

/cc @njuettner (your name was on the last PR for the namespace feature)

[rahtr]

Any updates on this? When can we merge it?

[stevehipwell]

@Raffo do you have any thoughts on this? It looks good to me and it'd make sense to get merged now and in the release I'm about to do if you're happy?

[stevehipwell]

/label tide/merge-method-squash

[Raffo]

@stevehipwell this works for me, I don't have too many opinions on how the helm chart should be configured.

[Raffo]

/lgtm
/approve

[k8s-ci-robot]

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