Many-To-Many with extra column

Hello,

how does one use this framework and the DAO to create a Many-To-Many table with an extra column, which can be accessed from the Entity class referencing the many-to-many table? Take the code from [here](https://github.com/JetBrains/Exposed/wiki/DAO#many-to-many-reference) for example, if I were to add another column to `StarWarsFilmActors`, how do I access it in `StarWarsFilm`? Because there I can only access `Actor`, but not `StarWarsFilmActors`.

I have found a similar issue (#180) which uses a hacky approach with an Entity, but this entity requires the table to have an Id, which is not a wise database-design decision, since the primary key of many-to-many relation tables has to consist of the two referenced tables, and an Id would make it possible to insert all kinds of invalid data into it.