Add docs for group issues page and group merge requests page

Closes #36533

See merge request !13678

Only require sidekiq-limit_fetch when enabled in settings

Closes #36253

See merge request !13715

Fix 500 errors in Atom feeds due to push events

Closes #36705

See merge request !13695

Make project selection dropdown consistent

See merge request !13562

Fix merge request head pipeline when pipeline has errors

Closes #36657

See merge request !13664

This gem allows Sidekiq jobs to be throttled. Unfortunately, it has a
side-effect: when we haven't enabled job throttling, it will still hit Redis a
lot (and miss, because nothing is configured).

As this setting already required a restart, ensure that the library is only
required when it's enabled.

Migrate CI/CD stages statuses

Closes #33453

See merge request !12584

Gitlab::Git deletions and simplifications

See merge request !13640

Use Gitaly 0.33.0

See merge request !13671

Remove CI API v1

See merge request !13652

Add `validates :key, uniqueness: { scope: :pipeline_schedule_id }` in `Ci::PipelineScheduleVariable` model

See merge request !13641

copy milestones and labels from issue when using create merge request button

Closes #35343

See merge request !13461

Issue 20900 remove ignore columns

See merge request !12166

Resolve "User profile activity feed contains broken image links"

Closes #36458

See merge request !13606

Bump rouge to 2.2.0

Closes #36554

See merge request !13633

Greatly reduce test duration for git_access_spec

See merge request !13675

Make username update fail if namespace update fails

Closes gitlab-com/support-forum#2316

See merge request !13642

Fix broken Yarn dependencies

Closes #33886 and #34944

See merge request !13614

Resolve "Failing karma tests for Chrome 60"

Closes #36517

See merge request !13646

Remove superfluous users bundle

See merge request !13684

Also, move the old linting docs to the new location.

Fixed issue boards closed list displaying empty label

Closes #36650

See merge request !13658

Refactor GPG docs

See merge request !13660

Update Create Project Getting Started

See merge request !13687

Fix Error 500s when attempting to destroy a protected tag

Closes #36013

See merge request !13692

Due to a missing `on_delete: :cascade`, users would hit the error that
looked like:

```
PG::ForeignKeyViolation: ERROR: update or delete on table "protected_tags"
violates foreign key constraint "fk_rails_f7dfda8c51" on table
"protected_tag_create_access_levels" DETAIL: Key (id)=(1385) is still
referenced from table "protected_tag_create_access_levels". : DELETE FROM
"protected_tags" WHERE "protected_tags"."id" = 1385
```

Closes #36013

1. Generating a GPG key
1. Signing commits
1. Associating a GPG key with Git