Serve the pinned copy to public viewers #7939

Task Summary

Part of #7828. With a version pinned, a workflow has two copies. This routes every read that
serves a viewer without granted access through the frozen one.

• The seam — WorkflowAccessResource.hasGrantedAccess(wid, uid): granted access, as
  opposed to being able to read a workflow only because it is public. An owner or a shared user
  keeps tracking the author's latest, because sharing is not publishing.
• One copy, not a set of fields — WorkflowPublishService.PublicCopy carries the name, the
  description, the content and the default view together, and publicCopyOf hands them out as a
  group, so no surface can serve the published graph under a title the author never published,
  or open a form view over a copy whose content carries no form.
• Everything on public show freezes with the graph. The title and the description are as
  public as the graph is: if only the graph froze, a report about a title could be answered by
  editing the title while the pinned copy still advertised it.
• Routed through it — opening a workflow, the hub's read of a public workflow, Clone,
  Duplicate, /workflow_name, /workflow_description, and the size a listing shows.
• The revision history is a door into the same room. Replaying a version folds deltas back
  from the author's current content, so listing or checking out versions would hand a public
  viewer the drafts the pin is holding back. canReadHistory keeps the history open to anyone
  with granted access, and to everyone while nothing is pinned — the public copy is then the
  author's latest, and its history is the history of what everyone can already see.

A workflow that follows the author's latest — every workflow today — is served exactly what it
is served now.

Covered by WorkflowPublishSpec: the published version reaching a stranger while the author
keeps their own working copy; opening a pinned workflow serving the whole copy, its own title,
description and view; a collaborator tracking the author's latest as they keep editing; clone
and duplicate taking the published copy, metadata included, while a private workflow still
clones its working copy; the size of each case; the revision history refused to a public viewer
while a pin is in place and kept open otherwise; and a public copy of a workflow that is not
public being refused rather than falling through.

Task Type

• Refactor / Cleanup
• DevOps / Deployment / CI
• Testing / QA
• Documentation
• Performance
• Other