Fixes #4395: Added `$checkAjax` parameter to `yii\web\Response::redirect()` to support default redirection behavior for AJAX/PJAX requests

Fixes #5480: Added defensive code to `yii\web\User::getIdentity()` to avoid potential infinite recursion

Fixes #4889: Application was getting into redirect loop when user wasn't allowed accessing login page. Now shows 403

close #5762

Fixes #5587: `json_encode` is now used with `JSON_UNESCAPED_SLASHES | JSON_UNESCAPED_UNICODE` where it makes sense, also it is now default for `Json::encode()`

If you don't want to install command-line utils globally, you have to specify it's paths.

    public $commands = [
        'styl' => ['css', '@app/node_modules/bin/stylus < {from} > {to}'],
    ];

close #5130

Fixes #5001: `yii\rest\CreateAction`, `yii\rest\UpdateAction` and `yii\rest\DeleteAction` should throw 500 error if the model operation returns false without validation errors

ensure it is one of the input values

fixes #4880