Enhanced parent filtering for better work item retrieval

Release notes

We've replaced the "epic" filter on listing pages with a more flexible "parent" filter that lets you filter by any parent work item, not just epics. This means you can now easily find child tasks by filtering on their parent issue, giving you better visibility into your work hierarchy and making it easier to track related work items.

Summary

Add Parent filter component to work items list UI as part of #536876 (closed). Make sure this filter is behind a feature flag work_items_list_parent_filter till all of the operators are working without performance issues.

Backend Support

See #548093 (closed)

Implementation Details

• Add Parent filter component to work items list UI (when backend is ready)
• A feature flag should control the filter on the UI
• Support filter operations:
  • Equals (specific parent)
  • Not Equals
  • Wildcard (any/none)
• Update filter state management and GraphQL queries
• Integrate with existing filter system

Acceptance Criteria

• Add a feature flag to control Parent filter
• Parent filter is available in epics list and project issue list
• All filter operations work correctly (equals, not equals, any/none)
• Filter handles epics and issues properly
• Filter integrates with existing filters
• Filter state is persisted in URL
• Unit tests added
• E2E tests updated

Related Issues

• Parent: #536876 (closed)
• Backend: #510269 (closed)
• Blocking: Backend performance issues (18.2 milestone)
• Iteration 2 for parent filter: #560430 (closed)
• Feature flag rollout issue: #560366 (closed)