Fix getting service IDs for status aggregation

Addresses [1].

Previously the query would always use UTC midnight, even after we
had switched to BST (+1h). We store timestamps as naive UTC in our
DB - without a timezone - but we want the query to work in terms
of GMT / BST so we adjust for that - BST midnight is 11PM in UTC.

[1]: https://github.com/alphagov/notifications-api/pull/3437#discussion_r791998690

app/dao/notifications_dao.py

@@ -46,7 +46,11 @@ from app.models import (
     NotificationHistory,
     ProviderDetails,
 )
-from app.utils import escape_special_characters, midnight_n_days_ago
+from app.utils import (
+    escape_special_characters,
+    get_london_midnight_in_utc,
+    midnight_n_days_ago,
+)
 
 
 def dao_get_last_date_template_was_used(template_id, service_id):
@@ -797,6 +801,9 @@ def get_service_ids_with_notifications_before(notification_type, timestamp):
 
 
 def get_service_ids_with_notifications_on_date(notification_type, date):
+    start_date = get_london_midnight_in_utc(date)
+    end_date = get_london_midnight_in_utc(date + timedelta(days=1))
+
     return {
         row.service_id
         for row in db.session.query(
@@ -804,7 +811,7 @@ def get_service_ids_with_notifications_on_date(notification_type, date):
         ).filter(
             Notification.notification_type == notification_type,
             # using >= + < is much more efficient than date(created_at)
-            Notification.created_at >= date,
-            Notification.created_at < date + timedelta(days=1)
+            Notification.created_at >= start_date,
+            Notification.created_at < end_date,
         ).distinct()
     }