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": "f225f846-9f8d-46b5-a423-e50a5519b12c",
    "type": "incident_event_functionalities",
    "attributes": {
      "incident_event_id": "35f3731a-87cb-43b6-b18f-1f3814d7c6c9",
      "functionality_id": "1a852f71-b324-4fc2-93f8-79c88f343f74",
      "status": "partial_outage"
    }
  }
}