Gumroad Ping Webhook Email with Rovela (2026): X-Gumroad-Signature + Sales API + Idempotency-Key
Verify optional X-Gumroad-Signature on the raw form body, re-fetch the sale via GET /v2/sales/{sale_id}, and send branded thank-you/delivery mail via Rovela POST /emails with Idempotency-Key = gumroad-sale-{sale_id}. Gumroad owns checkout; Rovela delivers. Distinct from Polar, Lemon Squeezy, Paddle, and Stripe webhook posts.