Many-to-Many relationships with composite ids fail

If you create two domain classes, both using composite ids and then try to establish a many-to-many relationship between the two, Grails will fail because it generates and invalid schema for the join table. Example:

class M2MBook implements Serializable {
Long isbn
Long edition
String title
static belongsTo = M2MAuthor
static hasMany = [authors:M2MAuthor]

static mapping =

}

class M2MAuthor implements Serializable {
Long family
Long child
String name
static hasMany = [books:M2MBook]

static mapping =

}

Grails will fail upon startup when creating the database. The error is: "org.hibernate.MappingException: Foreign key (FK124F769E7A4CB7FA:m2mauthor_books [m2mbook_id])) must have same number of columns as the referenced primary key (m2mbook [isbn,edition])"

The root problem is that GrailsDomainBuilder.bindDependentKeyValue doesn't properly identify that the composite key must be referenced and generates a mapping using simple id value. This is because shouldCollectionBindWithJoinColumn(property) returns false.

I've already attached a test case and a patch. I've also verified that the Hibernate test suite passes given my fix.

My fix is adding another clause to the if in GrailsDomainBuilder.bindDependentKeyValue that will handle the special case of a Many-to-Many with a composite key.