Use set of strings for SG IDs

modules/create-rds-postgres-tester/main.tf

@@ -16,7 +16,7 @@ resource "aws_sfn_state_machine" "create-tester-user" {
         "NetworkConfiguration": {
           "AwsvpcConfiguration": {
             "Subnets": ["${var.subnet_id}"],
-            "SecurityGroups": ["${var.db_clients_security_group_id}"],
+            "SecurityGroups": ["${join("\",\"", var.security_group_ids)}"],
             "AssignPublicIp": "ENABLED"
           }
         },

modules/create-rds-postgres-tester/variables.tf

@@ -26,11 +26,6 @@ variable "create_tester_user_task_pgrestore_workers" {
   description = "Number of pgrestore workers, one per CPU core"
 }
 
-variable "db_clients_security_group_id" {
-  type        = string
-  description = "ID of the security group that allows access to the RDS instance"
-}
-
 variable "db_connection_url_ssm_param_arn" {
   type        = string
   description = "ARN of SSM param which contains the connection URL for the Postgres database"
@@ -73,6 +68,11 @@ variable "rds_host" {
   description = "RDS host"
 }
 
+variable "security_group_ids" {
+  type        = set(string)
+  description = "IDs of the security groups that will be assigned to the network interface"
+}
+
 variable "subnet_id" {
   type        = string
   description = "ID of the subnet in which to run the extract/load ECS tasks and also in which to present the EFS mount point"