set secure flag for cookie

make/common/templates/nginx/nginx.https.conf

@@ -51,6 +51,9 @@ http {
       # When setting up Harbor behind other proxy, such as an Nginx instance, remove the below line if the proxy already has similar settings.
       proxy_set_header X-Forwarded-Proto $$scheme;
 
+      # Add Secure flag when serving HTTPS
+      proxy_cookie_path / "/; secure";
+
       proxy_buffering off;
       proxy_request_buffering off;
     }