metadata_collection of gromet_FN needs polymorphism

[kwalcock]

It looks like

        metadata_collection:
          description: |
            Table (array) of lists (arrays) of metadata,
            where each list in the Table-array represents the collection
            of metadata associated with a GroMEt object.
          type: array  # The Table of metadata_collection(s) (lists)
          items:
            type: array  # Collection (list) of metadata associated with a particular GroMEt object.
            items:
              $ref: "#/components/schemas/Metadata"

means that anything that includes an

      allOf:
        - $ref: '#/components/schemas/Metadata'

is allowed. In order for code generation to work, some things need to be added, including a discriminator and probably oneOf. See also https://swagger.io/docs/specification/data-models/oneof-anyof-allof-not/.