DataObject will need a URI property to support file downloading

[dehays]

The value of this new term will likely NOT be available when the DataObject metadata JSON is initially created - but will need to be present before the NMDC prototype application can support file downloads.

That is, when workflow execution provides DataObjects for output files we likely will not know yet where those files will be moved to be accessible from the application client interface. We can already begin to think about where the DataObject files output from processes need to be moved and begin updating those DataObjects