8FF - Subscription Box | Welcome + Retention + Churn + Replenishment

🔐 **Onboarding: API Keys & Environment Variables**

All HTTP requests rely on environment variables (never hard-coded):

`$env.BASE_API_URL` – Base URL of your subscriber/order API
`$env.API_KEY` – Bearer token for that API
`$env.EMAIL_API_URL` – Email service endpoint (e.g., Mailgun)
`$env.EMAIL_API_KEY` – Email service API key

**Sign-Up Links:**
- CRM / Subscriber DB: your choice (Airtable, custom API, …)
- Email: [Mailgun](https://www.mailgun.com/signup/)