Fix fragile tests (should use 'has_css' matcher instead of 'include')

[denny]

There are still several fragile tests that do something like expect( response.body ).not_to include a_test_string - this breaks occasionally when the test string is something that crops up in words used elsewhere in the page (e.g. 'tin' when using Faker::Science.elements). These tests should be made more specific using has_css to target the correct HTML element (and then hopefully I can remove the 'string_string'' kludge that's currently in a bunch of the factories).

[denny]

If you are a less experienced developer who is looking at this issue and thinking you'd like to try to take it on but you're not entirely confident, I would be happy to help you - whether that's help getting set up, more explanation of what needs doing, pairing on the code task itself, or anything else I can do to help.

In my day job I'm a lead developer who often mentors less experienced developers, and I'd love to use some of that experience to help people take their first steps into contributing to open source projects.

[denny]

Updated list of spec files that probably contain this issue:

denny@rocinante:~/ShinyCMS$ egrep -rc 'to +include' spec/requests plugins/*/spec/requests | grep -v 0 | sort
plugins/ShinyNewsletters/spec/requests/admin/editions_spec.rb:2
plugins/ShinyPages/spec/requests/admin/pages_spec.rb:3
plugins/ShinyPages/spec/requests/pages_spec.rb:4
plugins/ShinyProfiles/spec/requests/profiles_spec.rb:2
spec/requests/admin/site_settings_spec.rb:2
spec/requests/admin_spec.rb:2
spec/requests/admin/users_spec.rb:2
spec/requests/discussions_spec.rb:3
spec/requests/feature_flags_spec.rb:2
spec/requests/user_spec.rb:4