Fixes #4409: Upper case letters in subdirectory prefixes of controller IDs were not properly handled

fixed broken code block

- Upgrade the documentation to match filter code
- Fix bad default behavior with Access-Control-Allow-Credentials
- Fix missing "s" in header Access-Control-Request-Method / Access-Control-Allow-Methods

Fixes #4184: mentioned a safer way of using dummy cache that works in case of merging configs of advanced app

Fixes #4051: Renamed `yii\caching\GroupDependency` to `TagDependency` and added support for associating multiple tags to a single cached data item

fixes #4301

fix docs

It really should be: defining, attaching, using.