Warn if addon has no associated Github username

[klaases]

Fixes: #15063

Add an additional check to warn whether a 3rd party addon lacks a verified maintainer / associated Github username. We want to warn the user about addons without a maintainer as they may become deprecated over time.

Before:

Without verified maintainer (without extra warning):

$ ./out/minikube addons enable registry-aliases
❗  registry-aliases is a 3rd party addon and is not maintained or verified by minikube maintainers, enable at your own risk.
    ▪ Using image quay.io/rhdevelopers/core-dns-patcher
    ▪ Using image docker.io/alpine:3.11
    ▪ Using image gcr.io/google_containers/pause:3.1
🌟  The 'registry-aliases' addon is enabled

After:

Without verified maintainer (with extra warning):

$ ./out/minikube addons enable registry-aliases
❗  registry-aliases is a 3rd party addon and is not maintained or verified by minikube maintainers, enable at your own risk.
❗  registry-aliases does not currently have an associated maintainer.
    ▪ Using image quay.io/rhdevelopers/core-dns-patcher
    ▪ Using image docker.io/alpine:3.11
    ▪ Using image gcr.io/google_containers/pause:3.1
🌟  The 'registry-aliases' addon is enabled

Same before and after:

With verified maintainer:

$ ./out/minikube addons enable storage-provisioner
💡  storage-provisioner is an addon maintained by Google. For any concerns contact minikube on GitHub.
You can view the list of minikube maintainers at: https://github.com/kubernetes/minikube/blob/master/OWNERS
    ▪ Using image gcr.io/k8s-minikube/storage-provisioner:v5
🌟  The 'storage-provisioner' addon is enabled
16:10:53 jklaas/minikube
warn1 •2 ✭2

---

Reference:

Addons List

./out/minikube addons list

|-----------------------------|----------|--------------|--------------------------------|
|         ADDON NAME          | PROFILE  |    STATUS    |           MAINTAINER           |
|-----------------------------|----------|--------------|--------------------------------|
| ambassador                  | minikube | disabled     | 3rd party (Ambassador)         |
| auto-pause                  | minikube | disabled     | Google                         |
| csi-hostpath-driver         | minikube | disabled     | Kubernetes                     |
| dashboard                   | minikube | disabled     | Kubernetes                     |
| default-storageclass        | minikube | enabled ✅   | Kubernetes                     |
| efk                         | minikube | disabled     | 3rd party (Elastic)            |
| freshpod                    | minikube | disabled     | Google                         |
| gcp-auth                    | minikube | disabled     | Google                         |
| gvisor                      | minikube | disabled     | Google                         |
| headlamp                    | minikube | disabled     | 3rd party (kinvolk.io)         |
| helm-tiller                 | minikube | disabled     | 3rd party (Helm)               |
| inaccel                     | minikube | disabled     | 3rd party (InAccel             |
|                             |          |              | [info@inaccel.com])            |
| ingress                     | minikube | disabled     | Kubernetes                     |
| ingress-dns                 | minikube | disabled     | Google                         |
| istio                       | minikube | disabled     | 3rd party (Istio)              |
| istio-provisioner           | minikube | disabled     | 3rd party (Istio)              |
| kong                        | minikube | disabled     | 3rd party (Kong HQ)            |
| kubevirt                    | minikube | disabled     | 3rd party (KubeVirt)           |
| logviewer                   | minikube | disabled     | 3rd party (unknown)            |
| metallb                     | minikube | disabled     | 3rd party (MetalLB)            |
| metrics-server              | minikube | disabled     | Kubernetes                     |
| nvidia-driver-installer     | minikube | disabled     | Google                         |
| nvidia-gpu-device-plugin    | minikube | disabled     | 3rd party (Nvidia)             |
| olm                         | minikube | enabled ✅   | 3rd party (Operator Framework) |
| pod-security-policy         | minikube | disabled     | 3rd party (unknown)            |
| portainer                   | minikube | disabled     | 3rd party (Portainer.io)       |
| registry                    | minikube | disabled     | Google                         |
| registry-aliases            | minikube | enabled ✅   | 3rd party (unknown)            |
| registry-creds              | minikube | disabled     | 3rd party (UPMC Enterprises)   |
| storage-provisioner         | minikube | enabled ✅   | Google                         |
| storage-provisioner-gluster | minikube | disabled     | 3rd party (Gluster)            |
| volumesnapshots             | minikube | disabled     | Kubernetes                     |
|-----------------------------|----------|--------------|--------------------------------|

[spowelljr]

Can you run make generate-docs to update the translations

[klaases]

Can you run make generate-docs to update the translations

Yes, updated translation, thanks.

[k8s-ci-robot]

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