Allow the generated Insertable to work with manager references around custom row classes

[AhmedLSayed9]

If we try to build the generated code for the following tables:

class AnotherTable extends Table {
  IntColumn get id => integer().autoIncrement()();
}

@UseRowClass(Item, generateInsertable: true)
class Items extends Table {
  IntColumn get id => integer().autoIncrement()();
  IntColumn get anotherTable => integer().references(AnotherTable, #id)();
}

class Item {
  Item({required this.id});

  final int id;
}

It will throw a warning: This class used as a custom row class for which an insertable is generated. This means that it must define getters for all columns, but some are missing: anotherTable

It would be great if we can support generating toColumns which requires passing anotherTable to make that work.

So, user will be able to use toInsertable as following:

item.toInsertable(anotherTable: someId)

[simolus3]

A PR to change this behavior would be welcome, but this is not a priority for me. generateInsertable is meant for the case where you need some customization for a row class that roughly matches the structure drift expects. When that's not the case, you can always implement toColumns yourself.