Attaching CORS filter by default to RestGroup

[tunecino]

See yiisoft/yii2#11086 for details.

This is an issue that has been fixed in Yii 2.0 by suggesting a manual fix of order issue within docs because it was a BC.

I think it is the moment to make it right and add CORS by default here as the majority may need their REST apps to be consumed by browsers. Without the Access-Control-Allow-Origin even thrown errors will cause browser to trigger CORS preflight.

[samdark]

That is a good idea.

[rustamwin]

I think, all filters should be implemented as middleware :)

[samdark]

@rustamwin is correct.

[samdark]

Instead of controller it should be added to https://github.com/yiisoft/yii-rest/blob/master/src/RestGroup.php.

[samdark]

There's currently no CORS implementation. See https://trello.com/c/650bV6jy/116-implement-cors-middleware