Extracted page editor view data gathering to its own class for
alignment. Updated the data used in views as part of the process to use
view-specific variables instead of custom attributes added to models.
Also moved tinymce library loading so it's not loaded when not using the
wysiwyg editor.
- Added testing to cover warning cases.
- Refactored logic to be simpler and move much of the business out of
the controller.
- Added new message that's more suitable to the case this was handling.
- For detecting an outdated draft, checked the draft created_at time
instead of updated_at to better fit the scenario being checked.
- Updated some method types to align with those potentially being used
in the logic of the code.
- Added a cache of shown messages on the front-end to prevent them
re-showing on every save during the session, even if dismissed.
Tools seems to fit better since the classes were a bit of a mixed bunch
and did not always manage.
Also simplified the structure of the SlugGenerator class.
Also focused EntityContext on shelves and simplified to use session
helper.
