Backfill vulnerability_statistics.traversal_ids, archived

Why are we doing this work

As part of #512592 (closed) we're adding two new columns to the vulnerability_statistics table: traversal_ids and archived. These columns need to be backfilled using the projects and namespaces tables.

The backfill is implemented in a Batched Background Migration (BBM).

The backfill BBM should only start after the code has been changed to keep traversal_ids and archived in sync with the projects and namespaces table, and so this issue depends on Keep vulnerability_statistics.traversal_ids in ... (#513028 - closed) and Keep vulnerability_statistics.archived in sync (#513029 - closed).

Relevant links

• #512592 (closed)

Non-functional requirements

• Documentation
• Feature flag
• Performance: migration has to be fast enough
• Testing: migration has specs

Implementation plan

Add batched background migration (BBM) to backfill vulnerability_statistics.traversal_ids and archived columns, specs, and post-migration to enqueue that BBM.

Verification steps

Can be tested in the context of the group security dashboard of specific groups where remove_cross_join_from_vulnerabilities_projects_grade is enabled. See ProjectsGrades.grades_for using vulnerability_s... (!177892 - merged) and Resolve cross-join in ProjectsGrades.grades_for... (#513472 - closed).