Implement an advisory notice on the shelf permissions page regarding the lack of cascade #2876

When applying custom permissions to a shelf, using the "copy to books" options works for any existing books in that shelf but those same permissions don't seem to get applied to new books create within that shelf from then on unless you go back and use the button again.

Is this the intended result?

I'm on the latest installation (used the Ubuntu 20.04 script) not 100% on version number but will double check.