add content warning field to book

[jivey]

https://openstax.atlassian.net/browse/DISCO-342

I originally planned for this to be a snippet, but as far as I can tell, there's not a way to limit the association to a single snippet. I'm also unsure where on the form this should live... next to description seemed to make some sense, but I can move it around.

[mwvolo]

To limit the association to one snippet, you'd want to do something like this on the book model.

Also, create the model for the snippet, like this.

This solution work, but it means that we need to ensure the content is the same across all books (bigger content management lift).

Another option is to update the required books in the save method. I imagine this would look something like a filter for books that require the content warning and updating them all on save. (untested code example: Book.filter(subject__in=Subject.objects.get(name='Nursing').all())

I'd say it comes down to how many books this will be used on and the expectations of the behavior of this field.

[jivey]

@mwvolo Thanks for the links, that was a lot easier than I thought. I think this is ready for another look.

I noticed some of the snippets have an endpoint to return all (like http://127.0.0.1:8000/apps/cms/api/snippets/amazonbookblurb/?format=json) do you think I should add that for this as well?

[mwvolo]

@jivey I think you'll only need to do that if @RoyEJohnson is going to need to pull the warnings for some reason (to show on REX, for e.g.)

[mwvolo]

Looks good!
Can always add the endpoint for the snippet later if required.