### Context

For the split screen we have dedicated slots in the base.html.erb called `content_body`, `content_body_right` and `content_header` . When filled, the three parts look and behave as we want for split screen (including mobile) 
This was introduced for the new notification center split screen.

For full view pages like WorkPackages or the Documents full view, this layout however does not fit as it covers a completely different use case.

<br>

### Acceptance

This is the expected construct of these pages:

```text
|-------------------------------------------------
| | Tab1 | Tab 2 | ... |
| PageHeader | |
| | |
|---------------------------| |
| | |
| | |
| | some |
| some info | more |
| about the | details |
| object | |
| | |
| | |
|-------------------------------------------------
```

<br>

* Begin of the insertionThereEnd of the insertion Begin of the deletion Similar to the split screen, thereEnd of the deletion is a Begin of the insertioncomponentEnd of the insertion Begin of the deletion possibility to fill certain slotsEnd of the deletion which Begin of the insertioncan be used to achieve that page layoutEnd of the insertion Begin of the deletion then behave for each full view in the same wayEnd of the deletion

* The Begin of the insertionheader:

* can optionally go full width

* TheEnd of the insertion right side:

* goes full height Begin of the insertionif the header is not set to be full widthEnd of the insertion

* is optionally resizable

* On mobile:

* The two parts merge into one. The TabNav is extended by a new entry at the first position which contains the former left side

* Ideally, we would be able to keep the existing routing behavior