- classes.SiteCachePurger posts {kind, slug} with a bearer token to
golem15.journal.site_cache.purge_url, 2 s timeout, logged, never fails a save
- PurgeSiteCacheAfterCommit runs it through lagoon.AfterCommit
- Boot builds and publishes the purger from the two config keys
- categories FormAfterUpdate registers the purge; Postgres test proves
one authorized request after the commit