func hasPolymorphicRelation(tagSettings map[string]string) bool {
	if _, ok := tagSettings["POLYMORPHIC"]; ok {
		return true
	}

	_, hasType := tagSettings["POLYMORPHICTYPE"]
	_, hasId := tagSettings["POLYMORPHICID"]

	return hasType && hasId
}

func (schema *Schema) setRelation(relation *Relationship) {
	// set non-embedded relation