feat: Add support for service_ipv4_cidr for the EKS cluster

[nasuku]

PR o'clock

Description

This change adds support for service_ipv4_cidr that has been added to terraform-provider-aws last week.
( please see hashicorp/terraform-provider-aws#15505 )

This allows the user to specify the ipv4 CIDR for the k8s services (resolves #1056 )

Checklist

• CI tests are passing
• README.md has been updated after any changes to variables and outputs. See https://github.com/terraform-aws-modules/terraform-aws-eks/#doc-generation

[nasuku]

The linter failures (which are happening on top of tree) are fixed in a separate pr #1140 .

[pcantea]

Is there a rough time estimate of when this might get merged? Looks like a rather benign change, but it's blocking our prod EKS deployment :)

[im-nonedone]

@nasuku we forked you repo to use it. With the new Service IPv4 CIDR, we ran into --dns-cluster-ip issue. We were getting 172.20.0.10 as the cluster DNS on the pods, which is not the subnet we are using. This also needs to be looked into on bootstrap.sh in amazon-eks-ami.

As a workaround we specified this --dns-cluster-ip <ip> in bootstap_extra_args referenced in local.tf

[nasuku]

@im-nonedone thanks for mentioning it. Yes. I too was passsing the dns-cluster-ip in bootstrap_extra_args.
I felt that this was more like a bug/enhancement in bootstrap.sh than handling in terraform.
if no fix comes from aws, then may be, a separate PR which accepts dns_cluster_ip as another variable would be a better option.

[nasuku]

thanks for the review @barryib . Made changes per your suggestion and rebased to master branch.

[github-actions]

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