Specifically, send data versions of course_expired_message and
offer_html.
The rendered HTML is still being sent for now, until the learning
MFE is updated to consume the data objects.
This is for the frontend-app-learning MFE to consume and show an
alert when offer_html is defined.
I've also tweaked that html a bit to work better in an environment
that doesn't have LMS's exact css.
