We’ve seen in letters usability testing that people get stuck in a
“no-man’s land” when trying to go back from the _Send yourself a test_
page.
This was broken for two reasons:
- we hadn’t considered that a letter template without placeholder still
requires you to fill in
- we’ve changed subsequently made the _view template_ page the place
where you do your actions, rather than the (old) page with all the
templates shown
So this commit fixes it so that the back link always take you back to
the page you were previously on, and adds some more test cases so we
have all the scenarios accounted for.