attach method
Inserts a pivot row linking related to this parent.
pivot may name extra columns on the declared middle table. Near, far
and morph type columns are taken from the two rows and refused as
extras — a second value for the same key would silently disagree.
The target row is not inserted and not deleted.
Implementation
Future<void> attach(
TChild related, {
Map<String, Object?> pivot = const <String, Object?>{},
}) => _attachRow(related, pivot);