Creates an incident event functionality

curl --request POST \
  --url https://api.rootly.com/v1/events/{incident_event_id}/functionalities \
  --header 'Authorization: Bearer <token>' \
  --header 'Content-Type: application/vnd.api+json' \
  --data '
{
  "data": {
    "type": "incident_event_functionalities",
    "attributes": {
      "incident_event_id": "<string>",
      "functionality_id": "<string>",
      "status": "operational"
    }
  }
}
'

{
  "data": {
    "id": "b77457a2-8dd5-4acb-ba29-11c0770eeb8a",
    "type": "incident_event_functionalities",
    "attributes": {
      "incident_event_id": "ca982d2f-ddb5-474e-bb23-964aabb21cea",
      "functionality_id": "8fd0154a-e708-45f6-9e8d-66b050ff1c4c",
      "status": "partial_outage"
    }
  }
}