Move provider restriction into broadcast settings

This means we will have a much easier way of knowing what the settings
are for a broadcast service.

Note, we can just move data directly into the newer table as there is
nothing on the API or admin app that is putting data in the
`service_broadcast_provider_restriction` table, this was being done
manually for the few services that needed it.

tests/app/service/test_rest.py

@@ -19,7 +19,7 @@ from app.models import (
     Notification,
     Permission,
     Service,
-    ServiceBroadcastProviderRestriction,
+    ServiceBroadcastSettings,
     ServiceEmailReplyTo,
     ServiceLetterContact,
     ServicePermission,
@@ -280,11 +280,8 @@ def test_get_service_by_id(admin_request, sample_service):
 
 
 def test_get_service_by_id_returns_allowed_broadcast_provider(notify_db, admin_request, sample_service):
-    notify_db.session.add(ServiceBroadcastProviderRestriction(
-        service=sample_service,
-        provider='ee'
-    ))
-    notify_db.session.commit()
+    settings = ServiceBroadcastSettings(service=sample_service, channel="severe", provider="ee")
+    notify_db.session.add(settings)
 
     json_resp = admin_request.get('service.get_service_by_id', service_id=sample_service.id)
     assert json_resp['data']['id'] == str(sample_service.id)