This is a fix for this bug:
https://meta.discourse.org/t/-/133185?u=blake
where rails would throw a missing template error when trying to confirm
a new email address when you had two factor backup codes enabled.
Apparently this feature broke during this commit:
68d35b14f4
when a partial that contained a lot of javascript was removed most
likely because it didn't comply with our Content Security Policy, so as
a fix I rewrote the previous js functionality without using any
javascript and then added a spec to verify that the correct backup code
form is displayed when that page is loaded.
3b16eb7abb