Dereferencing/Inlining when fetching content

[EricWittmann]

We have implemented dereference for some artifact types. This now requires implementing support for JSON Schema in Data Models and adding the dereferencing capabilities there, since we're relying on external libraries like Vert.x JSON Schema.

[carlesarnal]

@EricWittmann This is done using external tools, without Data Models? Do you want to keep this open? In that case I think we should probably rephrase the wording here.