Docs: use MUST/SHOULD/etc. when describing checks

[agurgel-te]

What were you searching in the docs?

K8S001 uses the indicative mood to specify a degraded state:

The version skew between the control plane (API Server) and the data plane (kubelet) violates the Kubernetes version skew policy [...]
There is a version skew between the control plane (API Server) and the data plane (kubelet).

But K8S002 uses it to specify a desired state:

There are at least 3 replicas specified for the resource.

This led to some confusion when I first read about the checks.

Is this related to an existing documentation section?

https://clowdhaus.github.io/eksup/info/checks/

How can we improve?

Use the keywords specified in Best Current Practice 14 and incorporate the phrase specified by RFC 8174 near the top of the page.

Got a suggestion in mind?

I would rewrite K8S001 as follows:

The version skew between the control plane (API Server) and the data plane (kubelet) MUST NOT violate the Kubernetes version skew policy, either currently or after the control plane is upgraded. [Suggestions welcome on the "will violate after upgrade" part, which was difficult to recast.]

And K8S002 as follows:

There MUST be at least 3 replicas specified for the resource.

And version-dependent checks like K8S008 as follows:

With target version < v1.24, Pod volumes SHOULD NOT mount the docker.sock file.
With target version >= v1.24, Pod volumes MUST NOT mount the docker.sock file.

And all other checks accordingly.

Acknowledgment

• I understand the final update might be different from my proposed suggestion, or refused.