Pays an amountless bolt11 invoice with everything in the account, minus the Lightning routing fee. Used when an account holder wants to fully drain an account in one call without having to compute the sendable amount themselves.

The server:

Decodes the bolt11 and rejects any invoice that already has an amount baked in — the invoice must be amountless so the server can derive how much to send.

Minimum: the account balance must be ≥ 5 sats and must still cover the fee margin after the routing-fee estimate. Anything below that returns 400 insufficient balance after fees.

Optional webhook: pass webhookUrl and webhookSecret in the body to be notified when the payment settles.