Merge pull request #55 from skieffer/force-revalidate

m: Use "force revalidation" pattern for twin site conf

manage/topics/nginx/templates/nginx.conf

@@ -26,6 +26,13 @@ server {
     listen {{listen_on}}{{' ssl' if ssl else ''}};
     server_name {{twin_server_name}};
 
+    # We use the "force revalidation" pattern
+    #   https://developer.mozilla.org/en-US/docs/Web/HTTP/Caching#force_revalidation
+    # so that readers always get the latest version of each page.
+    # Nginx already serves `ETag` and `Last-Modified` headers by default, so we
+    # just need to add the `Cache-Control: no-cache` header.
+    add_header Cache-Control "no-cache";
+
     {% if ssl %}
     {% if hsts_seconds %}add_header Strict-Transport-Security "max-age={{hsts_seconds}};" always;{% endif %}
     ssl_certificate     /etc/nginx/ssl/cert;