refactor(notifications): align app structure with backend conventions

apps/notifications/tests/test_views.py

@@ -6,7 +6,8 @@ import pytest
 from django.utils import timezone
 from rest_framework.test import APIClient
 
-from apps.notifications import services, views
+from apps.notifications.api import views
+from apps.notifications.services import store as services
 from apps.notifications.services import RedisNotificationStore
 from apps.notifications.tests.test_services import FakePubSub, FakeRedis
 from apps.users.models import User