private/get_margin

Calculates net initial and maintenance margin for a subaccount before and after an optional simulated state change (position and/or collateral deltas), and whether that change would pass the margin requirement. Values are net margin — mark-to-market value minus the requirement — so positive means healthy. Does not take open-order margin into account. Margins use the subaccount's manager's params. Set is_delayed_liquidation to use its delayed-liquidation override instead, as order checks do; the request is rejected for a subaccount without one.