Common fields (mapping) for all datasets

[nickdos]

Placeholder issue to note down issues/ideas for mapping data fields across datasets.

• BPA resource_permissions (needs a common field name). Would be good to give NCBI data a generated value of public, so we can filter across all datasets on this field.
• Accession URL - cross-dataset URL to the resource landing page
• Sequence file type - fasta, etc.
• Sequence file URL - currently missing for NCBI data but present as url in the associatedSequences field in BPA

GBIF have a GH repo for managing and "publishing" custom DwC extensions (schemas) - https://github.com/gbif/rs.gbif.org - we should investigate how we could share our custom set of fields here...