Shows current and previous broadcasts. Does not add a page for viewing
an individual broadcast.
Broadcasts are split into live and previous.
Draft broadcasts are excluded from the dashboard.
This commit removes the code the puts areas into the session and instead
creates and then updates a draft broadcast in the database.
This is so we can avoid session-related bugs, and potentially having a
large session when we start adding personalisation etc.
Once a broadcast is ready to go it is set to `broadcasting` straight
away with no approval. We’ll revisit this as we learn more about how
users might want to manage who can create and approve broadcasts.
The tests are a bit light in terms of checking what’s on the page, but
clicking through the pages is probably good enough for now.
