Add missing id attribute

[realFlowControl]

Hey there 🖖

this PR adds the missing id attribute. I stumbled on this while creating a node pool, that needs the kube_id as an argument.

Kind regards
Florian

[yanndegat]

hi @realFlowControl

thanks for this contribution.

ids exported attributes are often forgotten in docs and this is a mistake, but if ever you encounter a similar situation in the future, know that all terraform resource / datasource have an "id" attribute, whatever the provider.

kind regards as well