Grails: multiple relationships between two domain objects

Question

I am trying to implement two different types of relationships between two domain classes in Grails.

Consider the following; I have two domain classes, an Author and Book

Answer 1

Modify Book domain class. Remove author mapping.

class Book{
   String title
   static belongsTo = [Author]
}

Look for the new table FAVORITE_BOOKS once clean and run-app.