Provenance capture defaults to off

[dimitri-yatsenko]

provenance.capture shipped defaulting to True. That makes 2.3.4 the only release on the 2.3 line where upgrading changes what an unchanged schema declares: every dj.Manual table declared after the upgrade gains a hidden nullable column.

Adding a column at declaration is a deployment's decision. jobs.add_job_metadata already defaults to False for exactly this reason, and the two settings do the same kind of thing, so defaulting capture on was inconsistent as well as disruptive.

The platform enables it per project through the usual channels — DJ_PROVENANCE_CAPTURE, the config file, or the secrets directory.

Nothing else changes. A table declared with capture on still records on insert; deploy.add_prov_column still retrofits a table declared without it; the insert path is unchanged.

A side effect worth noting: with capture off, a default install no longer reaches build_payload on insert, so the unmemoized _get_job_version call there costs nothing unless a deployment has turned both capture and version_method="git" on. Memoizing it is still worth doing — tracked from @ttngu207's review of #1555 — but it is no longer on a default path.

Verification

452 unit and 688 integration tests pass on MySQL and PostgreSQL. The provenance integration tests set capture = True in their fixture, so they still exercise the feature; the unit test that pinned the default now pins False.