"""Board sharing module.

Share-link mint / consume / revoke and the membership-acceptance flow.

Companion to [topix.collab](../collab/__init__.py):
  * `collab` is the real-time transport (how concurrent editors coordinate).
  * `sharing` is the social entry point (how anyone gets *into* a board to begin with).

See sharing-archi.md (local, not in repo) for the full design.
"""
