- Introduce restrict_user_defined_variables project setting
  and allow it to be set via API.
- Define policy for user defined variables.
- Inject user-defined variables consistently throughout
  the codebase.
- Allow user-defined variables to be set only by maintainers
  if the project setting is enabled.
- Allow passing variables from parent to child pipeline

Refactor folder structure for security dashboard GraphQL files

See merge request gitlab-org/gitlab!51117

Enable optional_code_owners_sections by default

See merge request gitlab-org/gitlab!51643

Cases to consider when using feature flags

See merge request gitlab-org/gitlab!50574

Remove unneeded index

See merge request gitlab-org/gitlab!51676

Update repository mirroring UI text

See merge request gitlab-org/gitlab!51311

Update pipeline alert text to be more readable

See merge request gitlab-org/gitlab!49575

Update toast position on set status

See merge request gitlab-org/gitlab!50886

CI: use commit SHA in persistent refspec

See merge request gitlab-org/gitlab!51208

A Git fetch refspec normally looks like 'refs/foo/bar:refs/qux/baz'.
In English that means: resolve 'refs/foo/bar' on the remote server,
fetch the object it points to, and create a local reference
'refs/qux/baz' that points to that thing.

However, since Git 1.8.3 (released in 2013) it is also allowed to
write '$COMMIT_SHA:refs/qux/baz'. What that does is: fetch object
$COMMIT_SHA from the server, and create a local 'refs/qux/baz' that
points to that thing.

This commit changes the refspec used for "persistent ref" CI fetches.
We already know what commit SHA persistent refs point to so there is
no need to have Git resolve the persistent ref again during a CI
build.

- add changelog

Enable multipart transfers for S3 copying

See merge request gitlab-org/gitlab!51267

This is a follow-up to
https://gitlab.com/gitlab-org/gitlab/-/merge_requests/50922. Multithreaded,
multipart transfers are only enabled if the file is above 5 GB or the
multipart chunk size is explicitly set.

We now set the chunk size to 10 megabytes (the AWS SDK default) to make
file copies faster.

This commit also updates fog-aws to v3.8.0 to work properly with server
side encryption parameters.

CHANGELOG: https://github.com/fog/fog-aws/blob/master/CHANGELOG.md

Implement declarative enums abstraction

See merge request gitlab-org/gitlab!50698

Update GraphqlExtractor return value to be original hash

See merge request gitlab-org/gitlab!51596

Merge branch '297364-flaky-test-spec-services-merge_requests-export_csv_service_spec-rb-29-mergerequests' into 'master'

test: Fix flaky expectations

See merge request gitlab-org/gitlab!51457

Merge branch '296976-the-open-list-in-boards-with-swimlanes-applied-is-mislabeled-as-backlog' into 'master'

Rename Backlog list to Open for Swimlanes

See merge request gitlab-org/gitlab!51539

Remove merge_ref_auto_sync flag

See merge request gitlab-org/gitlab!51624

Instead of spreading the enum information all around the codebase
between different modules like models and GraphQL types, we can set a
single source of the truth for the Enum values.

To do so, we should promote the enums to be first class members of the
project by giving them a new top level directory to live in.

Remove test_failure_history flag

See merge request gitlab-org/gitlab!51464

Remove github_import_pull_request_reviews feature flag

See merge request gitlab-org/gitlab!51334

Override tertiary button mix blend mode for darkmode

See merge request gitlab-org/gitlab!51349

Reverts !46222 to fix 500 error on project's edit page.

See merge request gitlab-org/gitlab!51662

Update gitlab-experiment to 0.4.5

See merge request gitlab-org/gitlab!51506

This makes two functionally similar but helpful improvements in terms of
more clarity and better behavior when circumventing existing codepaths.

Docs: Clarify merge train requirement for GitLab repo

See merge request gitlab-org/gitlab!51647

Fix issues with IDE commit to new branch

See merge request gitlab-org/gitlab!51654

This reverts commit fcc43e30.

Fix argument type for background migration

See merge request gitlab-org/gitlab!51475

Add Design Sprint Template to issue templates.

See merge request gitlab-org/gitlab!51226

Record action when namespace trial starts

See merge request gitlab-org/gitlab!49351

Add `gl-button` to move issue button in issue sidebar

See merge request gitlab-org/gitlab!51285