Added automatic generating of unique slug value to `yii\behaviors\Sluggable`
Default event for `yii\behaviors\Sluggable` with `unique` enabled changed to 'insert'.
`yii\behaviors\Sluggable` optimized
`yii\behaviors\Sluggable` simplified
`yii\behaviors\Sluggable::validateSlug()` fixed to respect updating record
merge with upstream
CHANGELOG updated
`yii\behaviors\Sluggable` adjusted
Update README.md
Merge pull request #4675 from klimov-paul/4630-sluggable

Fix #4630: automatic generating of unique slug value to `yii\behaviors\Sluggable`
Model parameter added to `yii\behaviors\Sluggable::uniqueSlugGenerator` callback
save some function calls on AR insert
fixed broken NOT condition in elasticsearch
improved IDE autocompletion for AR::find()

[ci skip]
Made error message encoding configurable for ActiveForm

Updated yii.activeform.js to use the encode option introduced in #4122.
Updated ActiveForm with new option encodeErrorSummary

fixes #4690, close #4691
Fixes #4607: AR model will throw an exception if it does not have a primary key to avoid updating/deleting data massively
added source map generation so that styling can be debugged easily.
Add rest-rate-limiting.md to translate into Russian
Translated rest-rate-limiting.md into Russian
Fixes #4701