Add post logout redirect uri

> Please provide us with the following information:
> ---------------------------------------------------------------

### This issue is for a: (mark with an `x`)
```
- [ ] bug report -> please search issues before submitting
- [x] feature request
- [ ] documentation issue or request
- [ ] regression (a behavior that used to work and stopped in a new release)
```

### Expected/desired behavior
> Ability to have custom redirect endpoint after logout that is different from redirect uri

### OS and Version?
> Windows 8, 10, or 11. Linux (which distribution). macOS (Mojave? Catalina? Big Sur? Monterey?)
Linux

### Versions
>

### Mention any other details that might be useful
Can be the same configuration option as REDIRECT_URI but for post logout. I have a custom combo architecture of Flask and Dash and I need to override the logout page.

> ---------------------------------------------------------------
> Thanks! We'll be in touch soon.

未指定檔案、測試或進入點。先定位 sample 的 logout 流程和目前的 REDIRECT_URI 設定，然後定義獨立的 logout 後重新導向選項應如何與 Flask 和 Dash 的組合搭配運作；完成的標準是 logout 可以使用不同於現有重新導向 URI 的自訂端點。

由索引模型根據 Issue 內容生成。