Add variancy information to reference response model

[Migaroez]

Task description

The *ReferenceResponseModel does not follow the same structure as an Item-model, especially around the name/state, where we for documents have all the variant names available on items.

In the front end, we would like to show the name/state of the current active variant which we currently do based on the variants array.

Approach

Since this mostly an output/client requirement, I decided to use existing domain logic that can fetch the additional data from a cached repository and combine it in the PresentationFactory.

A better solution will be able to be build once we make media and members variant so this information is relevant to all tracked references/relation types in the system and thus the repository queries can be updated to include this extra information

Testing

Create some documents and media with pickers and pick the different items on each other.
Query the endpoint. If an item is picked by a document, then that documents status and culture should be returned in the output

[nikolajlauridsen]

Minor nitpicks, otherwise looks good 👍

[nikolajlauridsen]

LGTM 👍