Triggered when a user unregisters for a calendar event

{
  "version": "0.0.1",
  "action": "calendar_event.user_unregistered",
  "triggered_at": "<string>",
  "custom_metadata": "<string>",
  "event": {
    "id": "<string>",
    "title": "<string>",
    "slug": "<string>"
  },
  "source": {
    "slack_workspace_id": "<string>",
    "slack_channel_id": "<string>"
  },
  "user": {
    "profile_id": "<string>",
    "created_at": "<string>",
    "preferred_name": "<string>",
    "first_name": "<string>",
    "last_name": "<string>",
    "email": "<string>",
    "slack_user_id": "<string>",
    "slack_is_admin": true,
    "slack_is_bot": true,
    "slack_first_name": "<string>",
    "slack_last_name": "<string>",
    "slack_image_72": "<string>",
    "slack_image_original": "<string>",
    "slack_profile": {
      "deprecated": true,
      "warning": "The slack_profile field object is deprecated and will be removed in a future release. Use the top-level slack fields instead.",
      "id": "<string>",
      "is_admin": true,
      "is_bot": true,
      "first_name": "<string>",
      "last_name": "<string>",
      "email": "<string>",
      "image_72": "<string>",
      "image_original": "<string>"
    },
    "profile_fields": "<string>"
  }
}