Use terraform to config GCP proxy setup

With terraform (https://terraform.io) we can convert most of the infrastructure setup into code. This simplifies setting up a new proxy as well as providing reproducibility in the setup, eliminating human errors as much as possible.

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=190634711

java/google/registry/proxy/terraform/example_config.tf

@@ -0,0 +1,35 @@
+terraform {
+  backend "gcs" {
+    # The name of the GCS bucket that stores the terraform.tfstate file.
+    bucket = "YOUR_GCS_BUCKET"
+    prefix = "terraform/state"
+  }
+}
+
+module "proxy" {
+  source = "../../modules"
+  proxy_project_name = "YOUR_PROXY_PROJECT"
+  nomulus_project_name = "YOUR_NOMULUS_GPROJECT"
+  gcr_project_name = "YOUR_GCR_PROJECT"
+  proxy_domain_name = "YOUR_PROXY_DOMAIN"
+}
+
+output "proxy_service_account_client_id" {
+  value = "${module.proxy.proxy_service_account_client_id}"
+}
+
+output "proxy_name_servers" {
+  value = "${module.proxy.proxy_name_servers}"
+}
+
+output "proxy_instance_groups" {
+  value = "${module.proxy.proxy_instance_groups}"
+}
+
+output "proxy_ip_addresses" {
+  value = {
+    ipv4 = "${module.proxy.proxy_ipv4_address}",
+    ipv6 = "${module.proxy.proxy_ipv6_address}"
+  }
+}
+