Define node/link transformations in JSON Schema

[pudo]

In order to transform JSON objects into a D3-style node/link network graph, we need to consider annotations in the JSON Schema which detail what types of JSON objects should be turned into nodes and which ones should be links.

We can re-use the schema files at: https://github.com/pudo/celestial-emporium
See also: https://github.com/uf6/ottograf

In a next iteration, we can also consider storing layout information (such as icons, size info, ...) in the JSON schema to apply as a default for entities on the graph.