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": "63c112aa-4c5b-405a-9df0-8f8a2f4a2ee2",
    "type": "incident_event_functionalities",
    "attributes": {
      "incident_event_id": "f562913c-eade-4456-b1ef-150a3da30839",
      "functionality_id": "ab2b9a3a-3c70-40ef-af66-260a706432b1",
      "status": "partial_outage"
    }
  }
}