Instead of just setting one side of the relation to null in the through
list, remove the rows entirely.
Remove only the relations which match the filters that have already been
set on the list.
This is consistent with the way ManyManyList works.
Also some small tidy-up (removing an unnecessary line break and an
unused "use" statement)
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
