Enable iteration charts feature flag by default

Also mention and link in the iteration docs page

doc/user/group/iterations/index.md

@@ -13,7 +13,7 @@ info: To determine the technical writer assigned to the Stage/Group associated w
 > - It's enabled on GitLab.com.
 > - It's able to be enabled or disabled per-group.
 > - It's recommended for production use.
-> - For GitLab self-managed instances, GitLab administrators can opt to [disable it](#disable-iterations). **(CORE ONLY)**
+> - For GitLab self-managed instances, GitLab administrators can opt to [disable it](#disable-iterations). **(STARTER ONLY)**
 
 Iterations are a way to track issues over a period of time. This allows teams
 to track velocity and volatility metrics. Iterations can be used with [milestones](../../project/milestones/index.md)
@@ -73,6 +73,19 @@ An iteration report displays a list of all the issues assigned to an iteration a
 
 To view an iteration report, go to the iterations list page and click an iteration's title.
 
+### Iteration burndown and burnup charts **(STARTER ONLY)**
+
+> - [Introduced](https://gitlab.com/gitlab-org/gitlab/-/issues/222750) in [GitLab Starter](https://about.gitlab.com/pricing/) 13.5.
+> - It was deployed behind a feature flag, disabled by default.
+> - [Became enabled by default](https://gitlab.com/gitlab-org/gitlab/-/merge_requests/45492) on GitLab 13.6.
+> - It's enabled on GitLab.com.
+> - It's able to be enabled or disabled per-group.
+> - It's recommended for production use.
+> - For GitLab self-managed instances, GitLab administrators can opt to [disable it](#disable-iteration-charts). **(STARTER ONLY)**
+
+The iteration report includes [burndown and burnup charts](../../project/milestones/burndown_and_burnup_charts.md),
+similar to how they appear when viewing a [milestone](../../project/milestones/index.md)
+
 ## Disable Iterations **(STARTER ONLY)**
 
 GitLab Iterations feature is deployed with a feature flag that is **enabled by default**.
@@ -97,6 +110,30 @@ Feature.disable(:group_iterations)
 Feature.disable(:group_iterations, Group.find(<group ID>))
 ```
 
+## Disable iteration charts **(STARTER ONLY)**
+
+GitLab iteration charts feature is deployed with a feature flag that is **enabled by default**.
+[GitLab administrators with access to the GitLab Rails console](../../../administration/feature_flags.md)
+can disable it for your instance. `:iteration_charts` can be enabled or disabled per-group.
+
+To enable it:
+
+```ruby
+# Instance-wide
+Feature.enable(:iteration_charts)
+# or by group
+Feature.enable(:iteration_charts, Group.find(<group ID>))
+```
+
+To disable it:
+
+```ruby
+# Instance-wide
+Feature.disable(:iteration_charts)
+# or by group
+Feature.disable(:iteration_charts, Group.find(<group ID>))
+```
+
 <!-- ## Troubleshooting
 
 Include any troubleshooting steps that you can foresee. If you know beforehand what issues

ee/app/controllers/groups/iterations_controller.rb

@@ -5,7 +5,7 @@ class Groups::IterationsController < Groups::ApplicationController
   before_action :authorize_show_iteration!, only: [:index, :show]
   before_action :authorize_create_iteration!, only: [:new, :edit]
   before_action do
-    push_frontend_feature_flag(:iteration_charts, group)
+    push_frontend_feature_flag(:iteration_charts, group, default_enabled: true)
     push_frontend_feature_flag(:burnup_charts, group, default_enabled: true)
   end
 

ee/app/controllers/projects/iterations/inherited_controller.rb

@@ -4,7 +4,7 @@ class Projects::Iterations::InheritedController < Projects::ApplicationControlle
   before_action :check_iterations_available!
   before_action :authorize_show_iteration!
   before_action do
-    push_frontend_feature_flag(:iteration_charts, project)
+    push_frontend_feature_flag(:iteration_charts, project, default_enabled: true)
     push_frontend_feature_flag(:burnup_charts, project, default_enabled: true)
   end
 

ee/app/controllers/projects/iterations_controller.rb

@@ -4,7 +4,7 @@ class Projects::IterationsController < Projects::ApplicationController
   before_action :check_iterations_available!
   before_action :authorize_show_iteration!
   before_action do
-    push_frontend_feature_flag(:iteration_charts, project)
+    push_frontend_feature_flag(:iteration_charts, project, default_enabled: true)
     push_frontend_feature_flag(:burnup_charts, project, default_enabled: true)
   end
 

ee/app/models/ee/iteration.rb

@@ -47,7 +47,7 @@ module EE
     end
 
     def burnup_charts_available?
-      ::Feature.enabled?(:iteration_charts, resource_parent)
+      ::Feature.enabled?(:iteration_charts, resource_parent, default_enabled: true)
     end
 
     private

ee/changelogs/unreleased/psi-enable-iteration-charts.yml

+---
+title: Add burndown and burnup charts to iteration report
+merge_request: 45492
+author:
+type: added

ee/config/feature_flags/development/iteration_charts.yml

@@ -5,4 +5,4 @@ rollout_issue_url: https://gitlab.com/gitlab-org/gitlab/-/issues/229046
 milestone: '13.4'
 type: development
 group: group::project management
-default_enabled: false
+default_enabled: true