Pure constructor: a tag (+ optional detail/instance/errors/type) → the canonical Problem Details body. Fills status + title from the frozen tables and a stable legacy error code. No I/O, no throwing.
status
title
error
Pure constructor: a tag (+ optional detail/instance/errors/type) → the canonical Problem Details body. Fills
status+titlefrom the frozen tables and a stable legacyerrorcode. No I/O, no throwing.