Function cron_parser 

pub fn cron_parser() -> CronParser

The ONE cron grammar Kopiur accepts: standard 5-field expressions. croner 3 defaults to optional seconds and year fields (6/7-field Quartz-style patterns would parse), which would silently widen the admission-validated CRD surface and break substitute_h’s positional field math — every parse in the workspace (webhook validator AND controller scheduler) must go through this parser so the grammar cannot drift between them.