Hello Kris,
I am not sure if I understood your question correctly, but let me try to answer it.
When you say integrate planned outage with stashboard, I understand it like this that you are going to set a blackout in some tool. Even the blackout begins, it will send an event (using API) to stashboard that will update the service status to something like "Under maintenance" or whatever.
If you want to schedule a blackout in Stashboard for a particular service, I am not aware how it is done. Never came across that functionality.
Regards,
Anu