KEP-1645: Fix typo in Upgrade / Downgrade Strategy section

[AnupamGhosh]

I think the missing word is "DNS" here as:

1. The Version Skew Strategy section in the same doc says: "Kube-proxy and DNS must be upgraded before new MCS API versions may be used."
2. The context of the paragraph discusses about DNS: "To take advantage of MCS DNS, the DNS provider must be upgraded..."

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[MrFreezeex]

Thanks for the fix! I think those are mostly from a time where MCS was supposed to be natively implemented by kube-proxy. So I think those paragraph could be either removed or potentially replaced by something explaining that this an out-of-tree API and this should be addressed by each implementations individually.

[MrFreezeex]

/ok-to-test

[lauralorenz]

I agree with @MrFreezeex, we can take out the entire paragraph in this PRR, except the one sentence that says

"To take advantage of MCS DNS, the DNS provider must be upgraded to a
version that implements the MCS spec. "

[AnupamGhosh]

Thanks @MrFreezeex & @lauralorenz for the feedback! I have removed kube-proxy as a requirement for upgrading MCS API and made the change to have a DNS provider that resolves multicluster service and a mcs-controller that implements the MCS API in the upgrade/downgrade & version skew section.
If the change looks good to you I will go ahead and edit the description and title of this PR.

[MrFreezeex]

TBH I am not sure we should even mention the DNS provider explicitly here. It's the responsibility of the implementation to handle DNS that and we never talk about a "DNS provider" in the rest of the KEP so this come in a weird way here.

I think in both cases if we want to explain something we could just mention that we provide some out of tree CRDs which follows Kubernetes best practices (as you also mentioned in the current PR) and that implementation should defined their own strategy and compatibility matrix with the CRD versions that we provide ~

[AnupamGhosh]

Yeah, I agree that the wording "DNS provider" falls out of line with the context of the KEP. However, there are two distinct implementations here:

1. The "MCS DNS implementation", which the KEP talks about in the Alpha -> Beta Graduation criteria.
2. An mcs-controller that implements the MCS API to create ServiceImport objects dynamically (mentioned in the Importing Services section).

I think being explicit about these two distinct implementations makes it clearer about which components need to be updated. What do you think?