Comment 4 for bug 2040314

Here's a branch that copies Garry's changes, but only for the "Send Test Email" button: https://git.evergreen-ils.org/?p=working/Evergreen.git;a=shortlog;h=refs/heads/user/sleary/lp2040314-opac-test-email-link-button

His testing notes in #1 still apply for email. We no longer need to enable username changes in the library settings to test this, since that button isn't changing.