Configure hosts for application

Note: the healthcheck endpoints are requested by IP, not domain, so we
need to specifically exclude them from the protection.

config/environments/production.rb

@@ -80,10 +80,10 @@
   config.active_record.dump_schema_after_migration = false
 
   # Enable DNS rebinding protection and other `Host` header attacks.
-  # config.hosts = [
-  #   "example.com",     # Allow requests from example.com
-  #   /.*\.example\.com/ # Allow requests from subdomains like `www.example.com`
-  # ]
+  config.hosts = [
+    /local-links-manager\..*gov.uk?/,
+  ]
+
   # Skip DNS rebinding protection for the default health check endpoint.
-  # config.host_authorization = { exclude: ->(request) { request.path == "/up" } }
+  config.host_authorization = { exclude: ->(request) { request.path.match?("^\/healthcheck") } }
 end