Use new API endpoint for scheduled job stats

Depends on:
- [ ] https://github.com/alphagov/notifications-api/pull/2984

app/models/service.py

@@ -151,6 +151,12 @@ class Service(JSONModel):
             return []
         return ScheduledJobs(self.id)
 
+    @cached_property
+    def scheduled_job_stats(self):
+        if not self.has_jobs:
+            return {'count': 0}
+        return job_api_client.get_scheduled_job_stats(self.id)
+
     @cached_property
     def invited_users(self):
         return InvitedUsers(self.id)