code: public ExtendedRelation addAttributesRelationship(String baseTableName,
  			String relatedAttributesTableName, String mappingTableName) {
  		return addRelationship(baseTableName, relatedAttributesTableName,
  				mappingTableName, RelationType.ATTRIBUTES);
  	}
docs: Adds an attributes relationship between the base table and related
  attributes table. Creates a default user mapping table if needed.
  
  @param baseTableName
  base table name
  @param relatedAttributesTableName
  related attributes table name
  @param mappingTableName
  mapping table name
  @return The relationship that was added
  @since 3.2.0