osdu_ingest - Make dataset optional inside "Data" block of JSON payload
In the current structure, "Data block" expects all 3 sections - work-product, work-product component and then Dataset.
During recent discussion with @todaiks and @Kateryna_Kurach , it transpired that Work-product component may simply refer to an existing Dataset record (created in previous step). so, we do not want to spend double effort to deal with Dataset record.
See collection 29 from Platform Validation. Steps 4c and 5a.