LEARNER-1894
This commit adds in course messaging for three use cases. First,
when the user is not signed in, the user is shown a message that
provides a link to sign in or register. If the user is signed in
but not enrolled, they are given a link to do so. If the user is
enrolled but the course has not yet started, they are shown a
message explaining when the course starts and shown a link (not
yet enabled) to add a reminder to their calendar.
The implementation defines a base message class and extends it
for the course home messages as well as the previously implemented
page level messages.
This includes several general enhancement in addition
to the fixes for unified_course_view:
1. Add support for default when no waffle flag defined.
2. Add support for table_blacklist to assertNumQueries.
3. Rename flag to 'course_experience.course_outline_page'.
4. Change flag default to True when it is not defined.
This sock sits at the bottom of both the home and the course content pages. It allows the user to click a 'Learn More' button to open a panel that allows the user to navigate to the upgrade checkout page. The sock is only shown for users that have not yet upgraded in a course that has a verification upgrade date that has not yet passed. Python tests cover the various course mode and upgrade dates.
