Merge pull request #4825 from nenad-zivkovic/master

[ci skip] Fixes typo in structure-assets.md
Fixes #4188: API exceptions are now exposing less data when YII_DEBUG is false

- If exception is internal it's always returned as HTTP 500 general purpose one.
- Type isn't exposed anymore.
Merge pull request #4826 from yiisoft/rest-dont-show-full-exceptions-in-production

Fixes #4188: API exceptions are now exposing less data when YII_DEBUG is false
Fixes #3283: Added `$checkAjax` to `yii\web\User::loginRequired()`
Fixes #4829: Removed `PARSING_ONLY` from `\yii\rest\UrlRule` to allow creating non-GET URLs for forms and tests
Sphinx test skipping code fixed
`yii\sphinx\ActiveQuery` fixed to be resuable.
`yii\sphinx\ActiveQuery` fixed to be resuable with 'match' condition.
Fixes typo in concept-configurations.md