Function build_complex_option_order 

pub fn build_complex_option_order(
    complex_strategy: ComplexOrderStrategyType,
    order_type: OrderTypeRequest,
    legs: Vec<OrderLegSpec>,
    price: Option<f64>,
    duration: OrderDuration,
    session: OrderSession,
    cancel_time: Option<String>,
) -> Result<Value>

Build a multi-leg complex option order (spread, iron condor, etc.).