Support export of metadata-only graphs

[ESapenaVentura]

Description of the issue

Based on a discussion with the UCSC wranglers, a team they are working collaboratively with requested the possibility of metadata-only submission due to the nature of the data (Needs to be kept in servers within their country)

The current way by which we do this it's not clear - We need to investigate. Best guess is we put a proposal and pass it to the other components, but we will need to determine by which entity these graphs are created from.

The original ops ticket is https://app.zenhub.com/workspaces/operations-5fa2d8f2df78bb000f7fb2b5/issues/gh/ebi-ait/hca-ebi-wrangler-central/1177