Draft: Resolve "Emails from Totem include a "My account" button that goes to "example.com""

Closes #113 (closed)

I had to change the SITE_ID variable from the default site (which I unfortunately can't delete) to 2, which is the ID for learn.staging.totem-project.org on staging, and the ID for learn.totem-project.org on production, so should be good.

Inspiration came from here: https://discuss.openedx.org/t/change-activation-email-header-links-from-linking-to-example-com/3264

And here: https://discuss.openedx.org/t/server-error-from-deleting-example-com-site-native/397