Merge branch 'docs-dev-ff' into 'master'

Docs: refactor FF dev docs

Closes #225491, #227806, #229265, and #233368

See merge request gitlab-org/gitlab!40126

doc/development/feature_flags/controls.md

+---
+type: reference, dev
+stage: none
+group: Development
+info: "See the Technical Writers assigned to Development Guidelines: https://about.gitlab.com/handbook/engineering/ux/technical-writing/#assignments-to-development-guidelines"
+---
+
 # Feature flag controls
 
 ## Access

doc/development/feature_flags/development.md

+---
+type: reference, dev
+stage: none
+group: Development
+info: "See the Technical Writers assigned to Development Guidelines: https://about.gitlab.com/handbook/engineering/ux/technical-writing/#assignments-to-development-guidelines"
+---
+
 # Developing with feature flags
 
 This document provides guidelines on how to use feature flags

doc/development/feature_flags/index.md

+---
+type: index, dev
+stage: none
+group: Development
+info: "See the Technical Writers assigned to Development Guidelines: https://about.gitlab.com/handbook/engineering/ux/technical-writing/#assignments-to-development-guidelines"
+---
+
 # Feature flags in development of GitLab
 
 [Feature Flags](../../operations/feature_flags.md)

doc/development/feature_flags/process.md

+---
+type: reference, dev
+stage: none
+group: Development
+info: "See the Technical Writers assigned to Development Guidelines: https://about.gitlab.com/handbook/engineering/ux/technical-writing/#assignments-to-development-guidelines"
+---
+
 # Feature flags process
 
 ## Feature flags for user applications

doc/user/feature_flags.md

+---
+stage: Release
+group: Progressive Delivery
+info: To determine the technical writer assigned to the Stage/Group associated with this page, see https://about.gitlab.com/handbook/engineering/ux/technical-writing/#designated-technical-writers
+---
+
+# GitLab functionality may be limited by feature flags
+
+> Feature flag documentation warnings were [introduced](https://gitlab.com/gitlab-org/gitlab/-/issues/227806) in GitLab 13.4.
+
+GitLab releases some features in a disabled state using [feature flags](../development/feature_flags/index.md),
+allowing them to be tested by specific groups of users and strategically
+rolled out until they become enabled for everyone.
+
+As a GitLab user, this means that some features included in a GitLab release
+may be unavailable to you.
+
+In this case, you'll see a warning like this in the feature documentation:
+
+CAUTION: **Warning:**
+This feature might not be available to you. Review the **version history** note
+on this page for details.
+
+In the version history note, you'll find information on the state of the
+feature flag, including whether the feature is on ("enabled by default") or
+off ("disabled by default") for self-managed GitLab instances and for users of
+GitLab.com. To see the full notes:
+
+1. Click the three-dots icon (ellipsis) to expand version history notes:
+
+   ![Version history note with FF info](img/version_history_notes_collapsed_v13_2.png)
+
+1. Read the version history information:
+
+   ![Version history note with FF info](img/feature_flags_history_note_info_v13_2.png)
+
+If you're a user of a GitLab self-managed instance and you want to try to use a
+disabled feature, you can ask a [GitLab administrator to enable it](../administration/feature_flags.md),
+although changing a feature's default state isn't recommended.
+
+If you're a GitLab.com user and the feature is disabled, be aware that GitLab may
+be working on the feature for potential release in the future.

doc/user/index.md

@@ -151,6 +151,10 @@ requests you're assigned to.
 you have quick access to. You can also gather feedback on them through
 [Discussions](#discussions).
 
+## Features behind feature flags
+
+Understand what [features behind feature flags](feature_flags.md) mean.
+
 ## Keyboard shortcuts
 
 There are many [keyboard shortcuts](shortcuts.md) in GitLab to help you navigate between