[Documentation] Adding precisely how to reference Kubernetes-CRD Middleware from other providers

[Aniem]

Do you want to request a feature or report a bug?

Feature

What did you expect to see?

A Kubernetes-crd Middleware lives in kubernetes, and as such, has a kubernetes name (for instance fooName) and a kubernetes namespace (for instance barNS))
If one needs to configure traefik via another provider a routing using that middleware (for instance kubernetes Ingress middleware with the current master branch (commit 7c430e5 in my case) ), one needs to give the correct traefik name of the namespace. After some testing and a view of the dashboard, it appears the correct name is barNS-fooName@kubernetescrd

As this might be unclear for people getting familiar, I suggest the rule ( <K8SNamespace>-<K8SName>@kubernetescrd) be written in the documentation.

Furthermore, and I'll probably create some bug reports on that later, this naming rule can generate collision, for instance if one has a namespace foo-bar containing a middleware baz and a namespace foo containing a middleware bar-baz. This might require to change to traefik naming rule for kubernetes-crd, possibly before getting that rule written down in the documentation. I suggest using a . as separator, as this character is forbidden in kubernetes objet names.

[bradjones1]

Refs #6322

[SantoDE]

Hello!

I just raised a PR for that #6719. Is that enough for your request?

[traefiker]

Closed by #6719.