Function build_order_configuration 

pub fn build_order_configuration(
    order_type: OrderType,
    side: OrderSide,
    quantity: Quantity,
    price: Option<Price>,
    trigger_price: Option<Price>,
    time_in_force: TimeInForce,
    expire_time: Option<UnixNanos>,
    post_only: bool,
    is_quote_quantity: bool,
    reduce_only: bool,
) -> Result<OrderConfiguration>

Builds the Coinbase OrderConfiguration payload from Nautilus order parameters.

Caller supplies the order type, side, quantity, optional price/trigger, time-in-force, optional expire time (required for GTD), post_only flag, and whether the quantity is denominated in the quote currency (only meaningful for MARKET orders).

Errors

Returns an error when the requested combination is not supported by Coinbase (e.g. STOP_MARKET, IOC LIMIT, missing required field).