V2: BYOS PDF attachments via external storage (Google Drive first)

[commrelayunit]

Summary

Specify a BYOS (bring your own storage) attachment model for RefHub so PDFs can be linked to publications without RefHub becoming a storage host.

Why

RefHub needs reference-manager-like PDF attachment behavior, but we do not want RefHub to own blob storage. The preferred direction is:

• RefHub manages metadata + attachment references
• users bring storage
• Google Drive is the first external storage provider target

Scope

• Define BYOS principle for attachments
• Specify Google Drive as first provider
• Describe architecture:
  • publication ↔ attachment record ↔ external file
  • likely extension/backend -> Drive -> publication link flow
• Explain why backend-mediated upload is preferred over direct extension Google auth for V1
• Define data model / API implications
• Define UX flows:
  • metadata only
  • metadata + PDF upload
  • missing/blocked PDF fallback
• Clarify ownership/auth model and open questions
• Place this in the V2 roadmap/docs structure

Deliverables

• spec doc under docs / V2 roadmap area
• roadmap update if needed
• practical rollout sequence

Notes

Goal is to avoid RefHub becoming a storage company by accident while still supporting linked PDFs cleanly.