Add healthcheck script for ECS container health checks

This calls the Rails /up endpoint to verify the application is running.

Also, use this new healthcheck script in the review app task definition

Author: whi-tw

.review_apps/ecs_task_definition.tf

@@ -107,7 +107,7 @@ resource "aws_ecs_task_definition" "task" {
       }
 
       healthCheck = {
-        command     = ["CMD-SHELL", "wget -O - 'http://localhost:3001/up' || exit 1"]
+        command     = ["CMD", "/app/bin/healthcheck"]
         interval    = 30
         retries     = 5
         startPeriod = 180

bin/healthcheck

@@ -0,0 +1,6 @@
+#!/bin/sh
+
+# Healthcheck script for ECS container health checks.
+# Makes a request to the Rails health endpoint and exits with appropriate code.
+
+wget --quiet --tries=1 --spider "http://localhost:${PORT:-3000}/up" || exit 1