Support partially-embargoed Dandisets

[jwodder]

This was spun off of #8, due to being blocked on implementation of dandi/dandi-archive#1772.

Once the feature is implemented in the Archive, backups2datalad will need to support partially-embargoed Dandisets (i.e., Dandisets in which some but not all assets are embargoed).

Questions that need answering (including re-checking the answers after the Archive implementation):

• What is the embargo_status of a partially-embargoed Dandiset?

  • Answer per Support embargoed dandisets #8 (comment): either OPEN or EMBARGOED

• How can a consumer of the API determine whether an individual asset is embargoed or not?

  • Answer per Support embargoed dandisets #8 (comment): By checking whether the "access" field of the metadata is "dandi:OpenAccess" or "dandi:EmbargoedAccess".

• When backing up open assets in an embargoed Dandiset, how (if at all) should the backups differ from backups of embargoed assets in the Dandiset?

• When backing up a blob asset in an embargoed Dandiset where the blob is also used by open assets in open Dandisets, what special consideration should be given to the asset?

  • Q: How can such blobs/assets be identified?
  • Yarik's comments in Support embargoed dandisets #8 indicate that he wants such assets to have their S3 URLs recorded.

• When backing up embargoed assets in an open Dandiset, how (if at all) should the backups differ from backups of open assets in the Dandiset?

  • Should such assets have their metadata stored in .dandi/assets.json?
  • Should such assets have their S3 URLs registered?