Default Apache on Heroku Redirects From https to http for Links Without Trailing Slash

I recently set up a Heroku app using the Apache and PHP buildpack. The Apache configuration on Heroku was most likely the default which, if it receives a request to a URL without a trailing slash, e.g.

http://www.foobar.com/about

it’ll redirect to

http://www.foobar.com/about/

That alone is fine. However, I was getting redirected from https to http, which was not fine. This is likely due to the presence of a load balancer in front of the Heroku app server with SSL/TLS being terminated at the load balancer. When a request to an https URL without a trailing slash like

https://www.foobar.com/about

the request was secure to the Heroku load balancer but from the load balancer to the Heroku app server, it must have been insecure, e.g.

http://www.foobar.com/about

At that point, Apache would redirect to

http://www.foobar.com/about/

and the user would end up going from https to http. To resolve this, and as a best practice, just force https on all URLs. This is easily done on Heroku using a .htaccess file with a redirect rule, in case your chosen server is Apache.