mutation BookAppointment($input: BookAppointmentInput!) {
  bookAppointment(input: $input) {
    id
    number
    status
    appointmentRemindersEnabled
    historical
    startAt
  }
}

{
  "input": {
    "requestId": "id",
    "estimatorUserId": "id",
    "startAt": "value",
    "endAt": "value"
  }
}

{
  "data": {
    "bookAppointment": {
      "id": "id",
      "number": 1,
      "status": "string",
      "appointmentRemindersEnabled": true,
      "historical": true,
      "startAt": "value"
    }
  }
}