Reads the optional `generation` cell by header name (REQUIRED_HEADERS is
not extended — REQ-IMP-001 backward-compat for older artifacts), parses
it through GENERATION_PATTERN (^\s*G?\s*(-?\d+)), and routes it into
PersonUpsertCommand.generation.
Out-of-range values (G 99, G -1) are skip-and-warned, never abort the
batch; the post-parse range guard mirrors the V70 CHECK constraint so
the DB never sees a value Bean Validation wouldn't accept.
Pinned with a parametrised CsvSource covering every shape from the
acceptance criteria plus a backward-compat test (artifact without a
generation column still imports, all upserts get generation=null).
Refs #689
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
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