Toggle pre-warmed domain auto-renewal

Opt the account in or out of automatic renewal for its purchased pre-warmed domains. Auto-renewal is OFF by default: pre-warmed domains are aged assets that otherwise retire at registrar expiry.

With auto-renewal on, expiring pre-warmed domains are charged as a one-off invoice (registrar cost rounded up plus $1 per domain, per year) about 7 days before expiry, and the domain is renewed only after the charge succeeds.