Storage: Utilize JSON-LD fully

[sondreb]

The plan is to use JSON-LD partially for the storage feature, appending the "@context" and "@type" fields to the signed document to use that to differentiate between types of collections.

This task is added to consider using it more fully, like for example that it appends signature at the bottom as suppose to how we manage it on our feature.

https://json-ld.org/playground/