Generates an activity report of GitHub events for a specified user. The report groups events by day, repository, and event type, providing an organized view of the user's activities over a specified date range.

• userName (required): The GitHub username for which to generate the activity report.
• startDate (optional): The start date of the activity report in YYYY-MM-DD format. If not provided, the report includes all events up to the endDate.
• endDate (optional): The end date of the activity report in YYYY-MM-DD format. If not provided, the report includes all events from the startDate onwards.

The API returns a JSON response body with the following structure:

{
  "YYYY-MM-DD": {
    "repository_name": {
      "event_type": [
        {
          "id": "event_id",
          "created_at": "event_timestamp",
          "payload": { /* event payload */ }
        },
        // More events...
      ]
    },
    // More repositories...
  },
  // More dates...
}