Variable InMessageAddToCart`Const`

InMessageAddToCart: MessageDefinition<{
    positions: {
        articleNumber: string;
        configurationId?: string;
        linePosition: number;
        quantity: number;
    }[];
}> = ...

The WidgetManager does handle this event under the hood via the addToCart handler in the constructor. Incoming request from the iframe to add items to the cart.