Design document for the Zenodo like DOI per dandiset

[yarikoptic]

A design doc composed with @djarecka to avoid dummy DOIs for dandisets

refs:

• Stop injecting "fake" DOIs into draft dandisets #1709
• Unpublished Dandisets display a DOI under Cite As #1932

TODOs

• complete initial pass
• seek review
• make explicit that DOI generation is optional overall, since LINC does not even need it (ref)
• potentially add a sequence diagram of interactions between user, archive, datacite across different stages of embargoed -> public dandisets

but could already be checked out by @dandi/archive-maintainers folks since overall idea is formulated already and some early concerns/questions could already be asked/answered