Many-to-Many mapping with attributes

Hello,
I have the following problem which I do not know how to solve.
I have "Candidates" as well as "Skills" which own have their own table and I want a many to many relationship between them where the "level" is an attribute of the table which links both Entities:

```kotlin
object Candidates: UUIDTable() {
val name = varchar("name", 50).index()
val age = short("age").nullable()
val created = datetime("created")
val updated = datetime("updated")
}

class Candidate (id: EntityID) : UUIDEntity(id) {
companion object : UUIDEntityClass(Candidates)
var name by Candidates.name
var age by Candidates.age
var skills by Skill via CandidateSkills
}

object CandidateSkills: Table() {
val candidate = reference("candidate", Candidates, onDelete = ReferenceOption.CASCADE).primaryKey(0)
val skillName = reference("skillName", Skills, onDelete = ReferenceOption.CASCADE).primaryKey(1)
val level = short("level")
}

object Skills: UUIDTable() {
val skillName = varchar("skill_name", 40).index()
}

class Skill(id: EntityID) : UUIDEntity(id) {
companion object : UUIDEntityClass(Skills)

var skillName by Skills.skillName
// How get this to work?
var level by CandidateSkill referencedOn CandidateSkills.level
}
```

The documentation does not mention how to reference such an attribute.

Could somebody help me please?

Best regards. Mike