curl --request GET \
  --url https://api.sprucecollective.co.uk/analytics/subscriptions/optimized \
  --header 'Authorization: <api-key>'

{
  "churn_analysis": {},
  "credit_analytics": {},
  "generated_at": "<string>",
  "period": "<string>",
  "subscription_metrics": {
    "active_subscribers_by_tier": {},
    "churn_rate": 123,
    "credit_usage_distribution": {},
    "credit_utilization_rate": 123,
    "expired_vs_used_ratio": {
      "expired_credits": 123,
      "ratio": 123,
      "used_credits": 123
    },
    "mrr": 123,
    "revenue_by_tier": {},
    "total_active_subscriptions": 123,
    "total_cancelled_subscriptions": 123,
    "user_engagement_correlation": {
      "engagement_correlation": 123,
      "high_engagement_users": 123,
      "low_engagement_users": 123
    }
  }
}