Consider supporting ActiveJob::Continuation as an alternative to job-iteration

[kwent]

Summary

Rails 8.1 introduces ActiveJob::Continuation (ActiveJob::Continuable), which provides built-in support for interruptible, resumable jobs with cursor-based progress tracking — functionality that closely overlaps with what job-iteration provides today.

Since maintenance_tasks depends on job-iteration for its core iteration/resumption engine, it would be worth considering whether ActiveJob::Continuation could serve as an alternative backend for Rails 8.1+ apps, potentially making the job-iteration dependency optional.

Key overlaps

Feature	job-iteration	ActiveJob::Continuation
Interruptible iteration	Yes	Yes (via step + checkpoint!)
Cursor-based resumption	Yes	Yes (set!, advance!, from:)
ActiveRecord collection iteration	Yes (build_enumerator)	Yes (find_each(start: step.cursor))
Nested collection support	Yes	Yes (array cursors)
Auto-retry after progress	Yes	Yes

Potential approach

• For Rails < 8.1: continue using job-iteration as today
• For Rails >= 8.1: allow tasks to use ActiveJob::Continuable instead, making job-iteration an optional dependency

Questions

• Is this something the team has already been thinking about given that this is a Shopify gem and job-iteration is also a Shopify gem?
• Would it make sense to support both backends, or would a full migration to ActiveJob::Continuation (with a minimum Rails version bump) be preferred long-term?