List sending domains

Returns the organization's sending domains, newest first. A namespace-scoped key lists only its namespace's domains; an organization-wide caller lists every domain, or one namespace's with namespaceId. Pass nextCursor back as cursor for the next page; it is null on the last page. sendable=true lists only domains a send can use now: active, and verified, or verified before and degraded since. Each row carries deliverability (bounce and complaint rates over the last 24 hours, the window the 5% bounce limit is enforced over) and series, the last 14 days of daily email sends attributed to the domain, oldest first.