provide a way to specify min/max required version for k8s cluster

[cppforlife]

it seems that some configuration providers (eg https://github.com/cloudfoundry/cf-for-k8s/blob/master/supported_k8s_versions.yml) will benefit from ability to specify min/max version of supported k8s. we should also provide a way to bypass this check for users that do not care about it.

apiVersion: kapp.k14s.io/v1alpha1
kind: Config
minimumRequiredVersion: 1.26.0 # kapp binary version

minimumRequiredKubernetesVersion: 1.18.0 # <--
maximumRequiredKubernetesVersion: 1.19.0 # <--

• figure out how this works with some k8s cluster versions that have all kinds of suffixes (what does kubectl version code do)

[brandonkal]

Those keys are very long. I would prefer something like:

kappVersion: >= 1.26.0
kubernetesVersion: 1.18.0-1.19.0

[rohitagg2020]

Few steps came out of discussion:

1. See how the other tools do it. Do they specify range or separate field for Min and Max version. Also check if multiple ranges are allowed.
2. Also, should we have a CLI flag to override the min and max K8s version mentioned.
3. Also refine it more as a good first issue.

[ranfysvalle02]

@rohitagg2020 - I'd like to help, but would like more details as to what the success criteria for this issue is. Could you please define what would need to be accomplished in order for this issue to be closed?