API: do not set rel="next" pagination header when no records found

Closes #36618

See merge request !13629

Fix external link to Composer website

Closes #36611

See merge request !13621

Make admin user actions dropdown consistent

See merge request !13630

Fixes the blown up emoji problem in notes

Closes #36448 and #36282

See merge request !13632

Properly explain when advanced Docker options were introduced

See merge request !13608

Docs: article - "Numerous undo possibilities in Git"

Closes gitlab-com/community-writers#40

See merge request !13513

And the link to the last page cannot be `page=0`.

Add specs that check the 'Link' header for the inclusion of:

 - rel="first"
 - rel="last"
 - rel="prev"
 - rel="next"

Fixes gitlab-org/gitlab-ce#36618

Related to gitlab-com/infrastructure#2532

Merge branch 'master' into 'docs-article-undo-things-in-git'

# Conflicts:
#   doc/articles/index.md

Move workflow/importing/ to user/project/import/

See merge request !13593

Prevent horizontal scrolling in new sidebar when collapsed

Closes #36608 and #36507

See merge request !13638

Allow all users to delete their account

Closes #36087

See merge request !13636

Backports EE mirror stuck handling feature…

See merge request !13627

Use grpc 1.4.5

Closes gitaly#468

See merge request !13597

Previously the user could not delete his own account unless signup was
enabled in the global settings. This was due to the fact that deleting
the user would also delete the issues and other items associated to him.
Deleting an user does not destroy essential data anymore, for this
reason we removed the `signup_enabled?` check.

Backports EE mirror stuck handling feature (https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/2628) to CE

Fixed height of group share dropdown

Closes gitlab-ee#3149

See merge request !13505

Improve migrations / background migrations testing strategy

Closes #36303

See merge request !13589

Resolve "Deleting of a GitLab Pages project results in "`PagesWorker.perform_in` cannot be called inside a transaction""

Closes #35072

See merge request !13631

Closes https://gitlab.com/gitlab-org/gitlab-ee/issues/3149

Fix project import to group when there are project milestones

Closes #35580

See merge request !13482

expose Referable#non_referable_inspect

See merge request !13613

Fix project templates and add docs

Closes #36492

See merge request !13563

`migrate!` helper triggers a migration that is under the test, so we
need to revert it before each subsequent example. This means that we
need to place it in `before(:each, :migration)` hook.

We still want to migrate everything up *after* each *context*, so in
otherwords we need to place migrate up helper in `before(:context,
:migration)`.

Fixed collapsed sidebar not showing fly-out menu

See merge request !13622

Upgrade grape to 1.0

Closes #36588

See merge request !13609

Fix help page version image spec

Closes #36592

See merge request !13605

Fix milestone sidebar collapse button

Closes #36453

See merge request !13620

The link pointed to the wrong page, this is corrected by both writing
the documentation and linking to that instead.

(internal)
Reference: https://gitlab.slack.com/archives/C0NFPSFA8/p1502791719000238