Test create_or_update! with unvalidated data

This should never happen in practice, but it's worth checking that
the method handles invalid data sensibly just in case.
Test that form is re-rendered when input is invalid
Monkey-patch ActionView's assert_template

It was permissively (and incorrectly) matching substrings
Test create_multiple with valid and invalid data

* Fix rendering of form if params are invalid
Check error is set for invalid data on confirmation
Make feature steps more self-explanatory
Test that versions are saved for multiple creation