curl --request GET \
  --url https://api.sprucecollective.co.uk/reports/user-growth \
  --header 'Authorization: <api-key>'

{
  "daily_data": [
    {
      "cumulative_users": 123,
      "date": "<string>",
      "growth_rate": 123,
      "new_users": 123,
      "rolling_avg_7d": 123
    }
  ],
  "summary": {
    "average_daily_growth": 123,
    "end_date_users": 123,
    "peak_day": {
      "date": "<string>",
      "new_users": 123
    },
    "start_date_users": 123,
    "total_cumulative_users": 123,
    "total_new_users": 123,
    "trend_percentage": 123
  }
}