- PgSQLSelectQuery implements common.WhereGrouper so x-custom-sql-or
is grouped with the client's own conditions on the pgx adapter too.
- Add a container test (opt-in via RESOLVESPEC_TEST_CONTAINERS=1) that
starts PostgreSQL with podman or docker and checks the hardening
against a real database: parenthesis escape, pg_sleep, catalog
subquery, stacked statements, x-custom-sql-or grouping and the
legacy behaviour when hardening is switched off.