My contact form is at the URI /contact-me (which means the page file is at /user/pages/03.contact-me/contact.md and the template is at /user/themes/br/templates/contact.html.twig).
I want to point the form action to /user/themes/br/php/mandrill_send.php but when I put that in the action field I end up at http://user/themes/br/php/mandrill_send.php which doesn't seem to be recognized as a page. It's certainly not a page as in /user/pages/.
How do I point to that action script in Grav? That is, how do I resolve Grav's routing structure to end up in the right place for the form action?