Added ability to provide a custom gridfield config.

[thepearson]

Allows config to be customized from the parent forms. I needed the ability to allow the user to select the type of class they wanted to create.

eg.

// This helper allows us to define the types of pages we can create.
$classCreator = new GridFieldAddNewMultiClass('buttons-before-right');
$classCreator->setClasses([RelationType1::class, RelationType2::class. RelationType3::class]);

$config = [
  new GridFieldHasOneButtonRow(),
  new GridFieldSummaryField("RelationType"),
  new GridFieldHasOneUnlinkButton($this, 'buttons-before-right'),
  $classCreator
];

$fields->removeByName("RelationTypeID");
$fields->addFieldToTab("Root.Main",
  HasOneButtonField::create($this, "RelationType", null, null, $config)
);

Might be of use to other folks.

[wilr]

IMHO we need keep the method signature the same for HasOneButtonField as GridField and have a the $config argument take a GridFieldConfig rather than change the argument to an array.

Other than that makes sense!

[thepearson]

Yeah cool, makes sense.