Add one_off filter when getting all notifications for a service

Added the option to filter by one_off messages to the DAO function
`get_notifications_for_service`. Previously, one-off notifications
were not returned - this has changed so that the default is for
one-off notifications to be returned. Also simplified the `include_jobs`
filter for this function.

The DAO function gets used in 3 places - for the V1 and V2 API endpoints,
which will now start to return one-off messages. It also gets used by
the admin app which needs to pass in `include_one_off=False` to the
`get_all_notifications_for_service` where we don't want one-off
notifications to show, such as the API message log page.

app/dao/notifications_dao.py

@@ -31,7 +31,6 @@ from app.models import (
     Service,
     Template,
     TemplateHistory,
-    KEY_TYPE_NORMAL,
     KEY_TYPE_TEST,
     LETTER_TYPE,
     NOTIFICATION_CREATED,
@@ -245,7 +244,8 @@ def get_notifications_for_service(
     include_jobs=False,
     include_from_test_key=False,
     older_than=None,
-    client_reference=None
+    client_reference=None,
+    include_one_off=True
 ):
     if page_size is None:
         page_size = current_app.config['PAGE_SIZE']
@@ -260,9 +260,11 @@ def get_notifications_for_service(
             Notification.created_at).filter(Notification.id == older_than).as_scalar()
         filters.append(Notification.created_at < older_than_created_at)
 
-    if not include_jobs or (key_type and key_type != KEY_TYPE_NORMAL):
-        # we can't say "job_id == None" here, because letters sent via the API still have a job_id :(
-        filters.append(Notification.api_key_id != None)  # noqa
+    if not include_jobs:
+        filters.append(Notification.job_id == None)  # noqa
+
+    if not include_one_off:
+        filters.append(Notification.created_by_id == None)  # noqa
 
     if key_type is not None:
         filters.append(Notification.key_type == key_type)