- One shared localizer for ValidationError and ForbiddenError, tested in
writeCRUDError's order; replaces the ForbiddenError-only one.
- Applied on the CRUD and relation service transactions, the detached bulk
branch, runAction, the record read (ShowRecord), and the reorder,
singleton and relation-options routes, which localized neither type.
- Only strings containing "::" are looked up, so translated text passes
through unchanged and logs no missing-key warning.
- Copy-on-write: the plugin's error value is never modified.
- README and backend docs describe the localized ValidationError.
