Activity feed: Summary on published snapshots

[chillu]

Overview

We are creating a datamodel to capture how changes affect objects in an ownership graph through the https://github.com/open-sausages/silverstripe-versioned-snapshots experimental module.

Design reference: https://projects.invisionapp.com/dsm/silver-stripe/silver-stripe/folder/components/5c68f96ffb26bb0018525d20

Acceptance Criteria

• As a content author working in a multi-author environment, I can tell which items were part of an immediate publish, and which ones were published based on previous snapshots
• I can tell which author performed each change, and when it was performed
• If multiple snapshots exist with unpublished changes, the next publish will list all owned items which have been published
• I can expand/collapse activity feeds for each snapshot entry
• There is different entries for adding and publishing items (since they might be attributed to different authors)
• When an item is published, any direct action within that snapshot is shown separately from "inherited changes" from other snapshots

Example

Example:

• Snapshot 0: Published
• Snapshot 1: Saved by AuthorA
• Direct changes
  • Add BlockA
  • Unpublish FileB
• Snapshot 2: Saved by AuthorB
• Direct changes
  • Changed BlockC
• Snapshot 3: Published by AuthorC
• Direct changes
  • Publish BlockA
  • Publish BlockC
  • Changed BlockD
  • Published BlockD
• Inherited changes
  • Add BlockA (by AuthorA)
  • Unpublish FileB (by AuthorA)
  • Changed BlockC (by AuthorB)

Notes

• Should work well with 50+ entries per snapshot, and 20 snapshots per paged view (might mean that we need to lazy load entries in each snapshot)