Create a single NAT gateway for all private subnets (#39)

* Create a single NAT gateway for all private subnets

* use official terraform source

* Create private subnets
- they are intended for the lanalyse and mdf hadoop cluster

* revert vpc module source as it fails tflint for unknown reasons

modules/core/variables.tf

@@ -66,7 +66,7 @@ variable "vpc_cidr" {
     default = "10.158.0.0/16"
 }
 
-// Convention is for the MSB of the third octect to be zero for public subnet and one for private
+// Convention is for the MSB of the third octet to be zero for public subnet and one for private
 // subnets.
 
 variable "vpc_public_subnets_cidr" {
@@ -78,7 +78,7 @@ variable "vpc_public_subnets_cidr" {
 variable "vpc_private_subnets_cidr" {
   description = "CIDR for each of the private subnets in the VPCs we want to create"
   type = "list"
-  default = []
+  default = ["10.158.240.0/24", "10.158.241.0/24", "10.158.242.0/24"]
 }
 
 variable "vpc_database_subnets_cidr" {

modules/core/vpc.tf

@@ -13,7 +13,8 @@ module "vpc" {
   private_subnets = "${var.vpc_private_subnets_cidr}"
   database_subnets = "${var.vpc_database_subnets_cidr}"
 
-  enable_nat_gateway = false
+  enable_nat_gateway = true
+  single_nat_gateway = true
   enable_vpn_gateway = false
   enable_dns_hostnames = true