url_helpers: Send the Content-Length header
url_helpers: Send the Content-Length header

In send_template() send a Content-Length header that is the number of
bytes in the processed html template.

Signed-off-by: Andrew Clayton <02e0a999c50b1f88df7a8f5a04e1b76b35ea6a88@digital-domain.net>

ac000/receiptomatic