This provides a mechanism for adjusting the behaviour of these
relations when building more complex data models.
For example the following example has a status field incorporates a
Status field into the relationship:
```php
function MyRelation() {
$rel = $this->getManyManyComponents(‘MyRelation’);
$rel = $rel->filter(‘Status’, ‘Active’);
$rel->addCallbacks()->add(function ($relation, $item, $extra) {
$item->Status = ‘Active’;
$item->write();
});
}
```
Introduces a new library dependency: http://github.com/sminnee/callbacklist
When many-many-through relations are queried, a joinRecord is set on
each DataObject in the list to provide the extra fields defined on
the connector object. This didn’t previously happen when the record
was first add()ed to a list. This fixes that bug.
* BUGFIX many many through not sorting by join table
* #8534 added docs to support many many sorting fix
* #8534 added test cases for many_many default sorting
* API Support many_many through polymorphic relations (from side only)
Fixes#7911Fixes#3136
* Add extra docs and allow optional arguments
* ENHANCEMENT Enable quiet to be turned off
* BUG Fix issue with manymanythroughlist duplication
