We want to upgrade to Rails 6! Notable changes:
Upgrade rspec-rails and ensure specs still pass
Change update_attributes calls to just ‘update’ to resolve deprecation warning (testing: make sure updates still work)
Specify that unique string validations (ie, admin logins, tag names) are not case sensitive (testing: make sure you can’t create duplicate tags with different cases)
Update the ActionMailer delivery job default to resolve deprecation warning (testing: make sure emails still get delivered)
Update configs to Rails 6 defaults, including using Zeitwerk as the code loader. Any problems with this should be visible in automated tests, but a general amount of smoke testing is still a good idea.
Not addressed: at some point before Rails 6.1, we need to redo the way autocomplete routes are handled, which will probably need to involve some reorganization of the controller.