We want to change cache keys for templates and broadcasts to include
their service ID. So cache keys should change from
`template-{template_id}-versions` to
`service-{service_id}-template-{template_id}-versions`.
The first step of this which needs to be deployed as a change first is
to delete both keys when updating service templates (even if they key is
not yet set). This means that when we release code in the next PR to
start setting the new key, we won't run into a case where either the old
or the new key can remain set with stale data.
This should make the pages slightly quicker to load, because Redis will
return the JSON string faster than the API.
The only change that can happen to a broadcast which doesn’t go through
the admin app is a broadcast ending at its scheduled time. So this could
result in a cached broadcast having a status of `broadcasting` when it
had in fact finished. We already account for this here though:
b2b58ec044/app/models/broadcast_message.py (L89-L94)
