feat: implement choice of AZs (#99)

* feat: implement choice of AZs

This PR introduce a choice for the AWS AZs, it's backward compatible,
and implement both the AZs definition in the VPC and the ROSA Cluster
itself

Related to
camunda/team-infrastructure-experience#411

* chore: add desc

modules/rosa-hcp/README.md

@@ -17,7 +17,9 @@
 
 | Name | Description | Type | Default | Required |
 |------|-------------|------|---------|:--------:|
-| <a name="input_availability_zones_count"></a> [availability\_zones\_count](#input\_availability\_zones\_count) | The number of availability zones to use for the cluster (minimum 2) | `number` | `2` | no |
+| <a name="input_availability_zones"></a> [availability\_zones](#input\_availability\_zones) | A list of availability zone names in the region. By default, this is set to `null` and is not used; instead, `availability_zones_count` manages the number of availability zones. This value should not be updated directly. To make changes, please create a new resource. | `list(string)` | `null` | no |
+| <a name="input_availability_zones_count"></a> [availability\_zones\_count](#input\_availability\_zones\_count) | The count of availability (minimum 2) zones to utilize within the specified AWS Region, where pairs of public and private subnets will be generated. Valid only when availability\_zones variable is not provided. This value should not be updated, please create a new resource instead. | `number` | `2` | no |
+| <a name="input_aws_availability_zones"></a> [aws\_availability\_zones](#input\_aws\_availability\_zones) | The AWS availability zones where instances of the default worker machine pool are deployed. Leave empty for the installer to pick availability zones from the VPC `availability_zones` or `availability_zones_count` | `list(string)` | `[]` | no |
 | <a name="input_cluster_name"></a> [cluster\_name](#input\_cluster\_name) | The name of the ROSA cluster to create | `string` | `"my-ocp-cluster"` | no |
 | <a name="input_compute_node_instance_type"></a> [compute\_node\_instance\_type](#input\_compute\_node\_instance\_type) | The EC2 instance type to use for compute nodes | `string` | `"m5.xlarge"` | no |
 | <a name="input_host_prefix"></a> [host\_prefix](#input\_host\_prefix) | The subnet mask to assign to each compute node in the cluster | `string` | `"23"` | no |

modules/rosa-hcp/rosa.tf

@@ -25,7 +25,8 @@ module "rosa_hcp" {
 
 
   replicas               = var.replicas
-  aws_availability_zones = module.vpc.availability_zones
+  aws_availability_zones = length(var.aws_availability_zones) > 0 ? var.aws_availability_zones : module.vpc.availability_zones
+
   aws_subnet_ids = concat(
     module.vpc.public_subnets, module.vpc.private_subnets,
   )
@@ -61,8 +62,10 @@ module "vpc" {
   source  = "terraform-redhat/rosa-hcp/rhcs//modules/vpc"
   version = "1.6.5"
 
-  name_prefix              = var.cluster_name
-  availability_zones_count = var.availability_zones_count
+  name_prefix = var.cluster_name
+
+  availability_zones_count = var.availability_zones != null ? null : var.availability_zones_count
+  availability_zones       = var.availability_zones
 
   vpc_cidr = var.vpc_cidr_block
 }

modules/rosa-hcp/vars.tf

@@ -41,10 +41,23 @@ variable "offline_access_token" {
 
 variable "availability_zones_count" {
   type        = number
-  description = "The number of availability zones to use for the cluster (minimum 2)"
+  description = "The count of availability (minimum 2) zones to utilize within the specified AWS Region, where pairs of public and private subnets will be generated. Valid only when availability_zones variable is not provided. This value should not be updated, please create a new resource instead."
   default     = 2
 }
 
+variable "availability_zones" {
+  type        = list(string)
+  description = "A list of availability zone names in the region. By default, this is set to `null` and is not used; instead, `availability_zones_count` manages the number of availability zones. This value should not be updated directly. To make changes, please create a new resource."
+  default     = null
+}
+
+
+variable "aws_availability_zones" {
+  type        = list(string)
+  description = "The AWS availability zones where instances of the default worker machine pool are deployed. Leave empty for the installer to pick availability zones from the VPC `availability_zones` or `availability_zones_count`"
+  default     = []
+}
+
 variable "vpc_cidr_block" {
   type        = string
   description = "value of the CIDR block to use for the VPC"