Mention management of `metadata.generation` and `status.observedGeneration`.

[evankanderson]

Document management of status.observedGeneration and client behavior from this comment.

TODO: experiment whether mutating webhooks could actually clear Conditions during PATCH of spec. If so, update webhooks and then we can remove this section.

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[dprotaso]

TODO: experiment whether mutating webhooks could actually clear Conditions during PATCH of spec. If so, update webhooks and then we can remove this section.

I believe Webhooks being invoked for spec changes can't update the status. They are separate invocations since /status is a subresource

[dprotaso]

@evankanderson do you still want this PR to merge? I didn't see a reply to @duglin's comment.