At the moment, we currently have broadcast services that have the
'broadcast' service permission in the DB but don't have a corresponding
row in the service_broadcast_settings table. It's important to give them
a row in this table because this will control which broadcast channel
their messages will go out on. All broadcast services will be expected
to have this row so we can then remove hardcoded defaults from our code
that currently set what channel a message should go out on.
Whilst, when this gets deployed, we will have released
https://github.com/alphagov/notifications-admin/pull/3794, which means
that when a service setting is changed via that form, they will get the
corresponding row in the service_broadcast_settings form, we don't want
to ask every developer to go and fill in this form for every service on
their local dev environment and also do the same to every service we
have in preview, staging and production. Therefore a migration is the
best way to backfill the data.
Note, I made the decision that a service that is in trial mode will be
given the 'severe' channel. This is because this is what most trial mode
services should have. Only the MNOs would ever really have a trial mode
service on the test channel. And given they are in trial mode, it is not
too risky to give them the 'severe' channel.
For services that are live though, although there are no services in
production that have the broadcast permission and are live, it is not
worth taking that risk and accidently setting that service to send an
alert out on the 'severe' channel. We play it say by choosing 'test'.
