Fix php warning when dice data isn't well formed when rebuilding dice counts
Adjust how dice data is appended to a post after a post-reply to avoid triggering additional full-entity saves
Drop support for displaying pre-v2.3.0 dice-data between add-on update and the add-on upgrade job finishing. Older versions used php serialized instead of json for the cached data.
Fix thread dice count would count non-visible posts
Track actual dice-count per thread instead of posts with dice
On install, will rebuild per-thread dice counts
When merging posts with embedded dice, old references in the surviving post will be updated to reference the surviving post instead of the deleted posts.
Notes: posts with embedded dice referencing the old posts will still not be valid