List all domain purchase orders with billing details

List all domain purchase orders on the account with billing and plan details.

Returns billing plan data only — no domain names, mailbox emails, or provisioning status. For those, use <code>GET /v1/domain</code> or <code>GET /v1/domain/orders/{orderId}</code>.

<code>hosts</code> is populated for InfraMail orders; <code>azureTenant</code> for Azure orders; both are null for other ESPs.