[BUG] Derivative Dataset schema is missing link to schema:Thing

[flaneuse]

Describe the bug
I created a schema on the Schema Editor derived from the NIAID Dataset schema. The resulting schema, downloaded from the DDE, is incapable of being visualized on the DDE Schema Registry. It looks like the connection from NDE:Dataset --> NIAID:Dataset --> schema:Dataset --> schema:CreativeWork --> schema:Thing is broken.

To Reproduce
Try to visualize https://raw.githubusercontent.com/NIAID-Data-Ecosystem/nde-schemas/39898d3ce324ff09dc7e9e95e1dcddd803fd0136/NDE_Dataset.jsonld. Error message:

    {
      "message": "Class \"https://discovery.biothings.io/view/NDE/Dataset\" has no path to the root \"<b class='text-primary'>schema:Thing</b>\" class",
      "error_type": "no_path_to_root",
      "record_id": "https://discovery.biothings.io/view/NDE/Dataset"
    },

Expected behavior
I'd expect something generated by the DDE Schema Editor to be visualizable in the DDE ;)

Screenshots

[flaneuse]

There are two issues here:

1. how to fix the schema json-ld so it correctly inherits the niaid:Dataset schema.
2. change the Schema Registry to correctly save the @context so deriving a schema based on a schema.org schema will be visualizable.