[install/infra] truncate EKS service node group to 58 chars + random suffix

EKS limits [iam role prefix lengths] to 38 characters, as the IAM role
length max is 64 characters and the random 26 character suffix eats up
most of the string length. As we're naming our clusters based on the
current branch these names could become quite long.

This commit removes this issue by creating a specific IAM role name and
creating our own unique IDs.

[iam role prefix lengths]: https://github.com/hashicorp/terraform-provider-aws/blob/v4.27.0/internal/service/iam/role.go#L29-L30

Author: adrienthebo

install/infra/modules/eks/kubernetes.tf

@@ -64,6 +64,13 @@ resource "aws_security_group" "nodes" {
   }
 }
 
+resource "random_string" "ng_role_suffix" {
+  upper   = false
+  lower   = true
+  special = false
+  length  = 4
+}
+
 module "eks" {
   source  = "terraform-aws-modules/eks/aws"
   version = "18.8.1"
@@ -91,6 +98,7 @@ module "eks" {
   eks_managed_node_group_defaults = {
     ami_type                   = "CUSTOM"
     iam_role_attach_cni_policy = true
+    iam_role_use_name_prefix   = false
     ami_id                     = var.image_id
     enable_bootstrap_user_data = true
     vpc_security_group_ids     = [aws_security_group.nodes.id]
@@ -102,6 +110,7 @@ module "eks" {
       enable_bootstrap_user_data = true
       instance_types             = [var.service_machine_type]
       name                       = "service-${var.cluster_name}"
+      iam_role_name              = format("%s-%s", substr("${var.cluster_name}-svc-ng", 0, 58), random_string.ng_role_suffix.result)
       subnet_ids                 = module.vpc.public_subnets
       min_size                   = 1
       max_size                   = 4
@@ -142,6 +151,7 @@ module "eks" {
     Workspaces = {
       instance_types = [var.workspace_machine_type]
       name           = "ws-${var.cluster_name}"
+      iam_role_name  = format("%s-%s", substr("${var.cluster_name}-ws-ng", 0, 58), random_string.ng_role_suffix.result)
       subnet_ids     = module.vpc.public_subnets
       min_size       = 1
       max_size       = 50