Add notes and update example to support GCP project as env vars (#78)

Signed-off-by: Jim Enright <[email protected]>

README.md

@@ -104,6 +104,8 @@ As outlined in the [Getting Started Docs for Google Terraform Provider](https://
 export GOOGLE_APPLICATION_CREDENTIALS=<location_of_gcp_sa_json_file>
 ```
 
+The Google project Id can be specified via the Google provider configuration variable or the `GOOGLE_PROJECT` environment variable. This is described in the [Google Provider Default Values Configuration](https://registry.terraform.io/providers/hashicorp/google/latest/docs/guides/provider_reference#provider-default-values-configuration) documentation.
+
 ## Local Development Environment
 
 See the [DEVELOPMENT.md](./DEVELOPMENT.md) file for instructions on how to set up an environment for local development of modules.

modules/terraform-cdp-deploy/examples/ex03-gcp-basic/main.tf

@@ -43,7 +43,6 @@ provider "google" {
   region  = var.gcp_region
 }
 
-
 module "cdp_gcp_prereqs" {
   source = "../../../terraform-cdp-gcp-pre-reqs"
 
@@ -66,7 +65,7 @@ module "cdp_deploy" {
 
   env_prefix          = var.env_prefix
   infra_type          = "gcp"
-  gcp_project_id      = var.gcp_project
+  gcp_project_id      = data.google_project.project.project_id
   region              = var.gcp_region
   public_key_text     = var.public_key_text
   deployment_template = var.deployment_template
@@ -100,3 +99,6 @@ module "cdp_deploy" {
     module.cdp_gcp_prereqs
   ]
 }
+
+# Use the Google Cloud Provider to retrieve GCP project details
+data "google_project" "project" {}

modules/terraform-cdp-deploy/examples/ex03-gcp-basic/variables.tf

@@ -20,7 +20,9 @@ variable "env_prefix" {
 
 variable "gcp_project" {
   type        = string
-  description = "Region which Cloud resources will be created"
+  description = "Region which Cloud resources will be created. Can also be set via gcloud project default or environment variable."
+
+  default = null
 }
 
 variable "gcp_region" {