add subnet tags

dns_zones.tf

@@ -136,6 +136,22 @@ resource "aws_vpc" "vpc" {
     { "Name" = "vpc0-dummy" },
   )
 }
+# Tag existing subnets for EKS
+# Container subnets under data.aws_subnets.container-subnets
+# Load Balance subnets under data.aws_subnets.lb-subnets
+resource "aws_ec2_tag" "container-subnets" {
+  for_each    = toset(data.aws_subnets.container-subnets.ids)
+  resource_id = each.value
+  key         = "kubernetes.io/cluster/${var.cluster_name}"
+  value       = "shared"
+}
+
+resource "aws_ec2_tag" "lb-subnets" {
+  for_each    = toset(data.aws_subnets.lb-subnets.ids)
+  resource_id = each.value
+  key         = "kubernetes.io/role/internal-nlb"
+  value       = "1"
+}
 
 #### This is the correct way, it's commented because
 #### the module is throwing an error on the for_each