Actually that was the part that makes everything hard.
Also we have the same thing for type mapping which was the most challenging part in the project for the moment.
You could see how to use it [here](https://github.com/amirsh/slick/blob/type-providers/codegen/slick-testkit/src/test/scala/scala/slick/test/jdbc/TypeProviderTest.scala#L195) and how to configure it from [here](https://github.com/amirsh/slick/blob/type-providers/codegen/slick-testkit/config/CustomTyping.scala)