Merge branch 'docs-kp-add-epic-work-items-page' into 'master'

Add Epic Work Item documentation page

See merge request https://gitlab.com/gitlab-org/gitlab/-/merge_requests/158286



Merged-by: Lysanne Pinto <lpinto@gitlab.com>
Approved-by: Lysanne Pinto <lpinto@gitlab.com>
Reviewed-by: Marcin Sedlak-Jakubowski <msedlakjakubowski@gitlab.com>
Reviewed-by: Lysanne Pinto <lpinto@gitlab.com>
Co-authored-by: Kushal Pandya <kushal@gitlab.com>

doc/user/group/epics/epic_work_items.md

+---
+stage: Plan
+group: Product Planning
+info: To determine the technical writer assigned to the Stage/Group associated with this page, see https://handbook.gitlab.com/handbook/product/ux/technical-writing/#assignments
+---
+
+# Test a new look for epics
+
+DETAILS:
+**Status:** Experiment
+
+> - [Introduced](https://gitlab.com/groups/gitlab-org/-/epics/9290) in GitLab 17.2. This feature is an [experiment](../../../policy/experiment-beta-support.md#experiment).
+
+FLAG:
+On self-managed GitLab, by default this feature is not available.
+To make it available, an administrator can enable the feature flags listed in [Feature flags](#feature-flags).
+On GitLab.com and GitLab Dedicated, this feature is not available. This feature is available for testing, but not ready for production use.
+
+DISCLAIMER:
+This page contains information related to upcoming products, features, and functionality.
+It is important to note that the information presented is for informational purposes only.
+Please do not rely on this information for purchasing or planning purposes.
+The development, release, and timing of any products, features, or functionality may be subject
+to change or delay and remain at the sole discretion of GitLab Inc.
+
+WARNING:
+This project is still in the experimental stage and could result in corruption or loss of production data.
+If you would like to enable this feature with no consequences, you are strongly advised to do so in a test environment.
+
+<!-- When epics as work items are made GA, incorporate this content into epics/index.md and redirect
+this page there -->
+
+We're working on changing how epics look by migrating them to a unified framework for work items to better
+meet the product needs of our Agile Planning offering.
+
+For more information, see [epic 9290](https://gitlab.com/groups/gitlab-org/-/epics/9290) and the
+following blog posts:
+
+- [First look: The new Agile planning experience in GitLab](https://about.gitlab.com/blog/2024/06/18/first-look-the-new-agile-planning-experience-in-gitlab/) (June 2024)
+- [Unveiling a new epic experience for improved Agile planning](https://about.gitlab.com/blog/2024/07/03/unveiling-a-new-epic-experience-for-improved-agile-planning/) (July 2024)
+
+## Related topics
+
+- [Work items development](../../../development/work_items.md)
+
+## Feature flags
+
+To try out this change on a self-managed instance of GitLab, enable the following feature flags. Because this is an experimental
+feature, **it is strongly advised to enable the feature flags on a new group that does not contain any critical data**.
+
+|Flag|Description|Actor|Status|
+|---|---|---|---|
+|`work_item_epics`| Consolidated flag that contains all the changes needed to get epic work items to work for a given group. |Group|**Required**|
+|`sync_work_item_to_epic`| Synchronizes data from a legacy epic to a corresponding work item. |Group|**Required**|
+|`work_items_rolledup_dates`| Calculates the start and due dates in a hierarchy for work items. |Group|**Required**|
+|`epic_and_work_item_labels_unification`| Delegates labels between epics and epic work item. |Group|**Required**|
+|`epic_and_work_item_associations_unification`| Delegates other epic and work item associations. |Group|**Required**|
+|`epic_and_work_item_notes_unification`| Delegates notes between epics and work item. |Group|**Required**|