[Feature flag] Removal of `sidebar_refactor` flag

What

Remove the :sidebar_refactor feature flag.

Owners

• Team: Create::Editor
• Most appropriate slack channel to reach out to: #g_create_editor
• Best individual to reach out to: @dmishunov, @fjsanpedro

Expectations

What are we expecting to happen?

What might happen if this goes wrong?

What can we monitor to detect problems with this?

Beta groups/projects

If applicable, any groups/projects that are happy to have this feature turned on early. Some organizations may wish to test big changes they are interested in with a small subset of users ahead of time for example.

• gitlab-org/gitlab project
• gitlab-org/gitlab-com groups
• ...

Roll Out Steps

• Enable on staging (/chatops run feature set feature_name true --staging)
• Test on staging
• Ensure that documentation has been updated
• Enable on GitLab.com for individual groups/projects listed above and verify behaviour (/chatops run feature set --project=gitlab-org/gitlab feature_name true)
• If it is possible to perform an incremental rollout, this should be preferred. Proposed increments are: 10%, 50%, 100%. Proposed minimum time between increments is 15 minutes.
• Coordinate a time to enable the flag with the SRE oncall and release managers
  • In #production mention @sre-oncall and @release-managers. Once an SRE on call and Release Manager on call confirm, you can proceed with the rollout
• Announce on the issue an estimated time this will be enabled on GitLab.com. Note: Once a feature rollout has started, it is not necessary to inform @sre-oncall/@release-managers at each stage of the gradual rollout.
• Enable on GitLab.com by running chatops command in #production (/chatops run feature set feature_name true)
• Cross post chatops Slack command to #support_gitlab-com (more guidance when this is necessary in the dev docs) and in your team channel
• Announce on the issue that the flag has been enabled
• Remove feature flag and add changelog entry. Ensure that the feature flag definition YAML file has been removed in the same MR that is removing the feature flag from the code
• After the flag removal is deployed, clean up the feature flag by running chatops command in #production channel

Rollback Steps

• This feature can be disabled by running the following Chatops command:

/chatops run feature set --project=gitlab-org/gitlab feature_name false

Testing

Please make sure package-and-qa job is passing before enabling the feature flag by default. Multiple E2E tests that use sidebar will need to be updated. If the feature is enabled initially on Staging only please limit it to a particular group/project to avoid affecting QA runs on Staging, if it is not possible please reach out to the SET (@a_mcdonald) to skip the affected tests on that environment beforehand.