Add example for IRSA and cluster-autoscaler (#710)

* Add example for IRSA

* remove unused SGs

* remove helm setup part

* simplification and use module

* fix fmt error

* remove unused resource

examples/irsa/irsa.tf

@@ -0,0 +1,57 @@
+module "iam_assumable_role_admin" {
+  source                        = "terraform-aws-modules/iam/aws//modules/iam-assumable-role-with-oidc"
+  version                       = "~> v2.6.0"
+  create_role                   = true
+  role_name                     = "cluster-autoscaler"
+  provider_url                  = replace(module.eks.cluster_oidc_issuer_url, "https://", "")
+  role_policy_arns              = [aws_iam_policy.cluster_autoscaler.arn]
+  oidc_fully_qualified_subjects = ["system:serviceaccount:${local.k8s_service_account_namespace}:${local.k8s_service_account_name}"]
+}
+
+resource "aws_iam_policy" "cluster_autoscaler" {
+  name_prefix = "cluster-autoscaler"
+  description = "EKS cluster-autoscaler policy for cluster ${module.eks.cluster_id}"
+  policy      = data.aws_iam_policy_document.cluster_autoscaler.json
+}
+
+data "aws_iam_policy_document" "cluster_autoscaler" {
+  statement {
+    sid    = "clusterAutoscalerAll"
+    effect = "Allow"
+
+    actions = [
+      "autoscaling:DescribeAutoScalingGroups",
+      "autoscaling:DescribeAutoScalingInstances",
+      "autoscaling:DescribeLaunchConfigurations",
+      "autoscaling:DescribeTags",
+      "ec2:DescribeLaunchTemplateVersions",
+    ]
+
+    resources = ["*"]
+  }
+
+  statement {
+    sid    = "clusterAutoscalerOwn"
+    effect = "Allow"
+
+    actions = [
+      "autoscaling:SetDesiredCapacity",
+      "autoscaling:TerminateInstanceInAutoScalingGroup",
+      "autoscaling:UpdateAutoScalingGroup",
+    ]
+
+    resources = ["*"]
+
+    condition {
+      test     = "StringEquals"
+      variable = "autoscaling:ResourceTag/kubernetes.io/cluster/${module.eks.cluster_id}"
+      values   = ["owned"]
+    }
+
+    condition {
+      test     = "StringEquals"
+      variable = "autoscaling:ResourceTag/k8s.io/cluster-autoscaler/enabled"
+      values   = ["true"]
+    }
+  }
+}