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": "24c6936c-72f2-44f3-af4d-b66d132f32b3",
    "type": "incident_event_functionalities",
    "attributes": {
      "incident_event_id": "705a8865-8136-44e2-a174-70cc7ef1335a",
      "functionality_id": "c64c8250-c5da-463c-aac8-15314bd971c6",
      "status": "partial_outage"
    }
  }
}