The NotificationService has to do quite a lot of work to calculate the
recipients for an email. Where possible, we should try to avoid doing this in an
HTTP request, because the mail are sent by Sidekiq anyway, so there's no need to
schedule those emails immediately.

This commit creates a generic Sidekiq worker that uses Global ID to serialise
and deserialise its arguments, then forwards them to the NotificationService.
The NotificationService gains an `#async` method, so you can replace:

    notification_service.new_issue(issue, current_user)

With:

    notification_service.async.new_issue(issue, current_user)

And have everything else work as normal, except that calculating the recipients
will be done by Sidekiq, which will then schedule further Sidekiq jobs to send
each email.

Add documentation about resetting the Runner registration token

See merge request gitlab-org/gitlab-ce!18296

Migration cleanup for merge request's commit_count (rev 1)

See merge request gitlab-org/gitlab-ce!17567

Align project avatar on small viewports

Closes #36585

See merge request gitlab-org/gitlab-ce!18513

* processes any pending records which are not migrated yet
* bumps import_export version because of new commits_count attribute
* removes commits_count fallback method

Backport dev env check for storage settings deprecation

See merge request gitlab-org/gitlab-ce!18461

Do not preload settings

See merge request gitlab-org/gitlab-ce!18566

Mock Pager in Karma tests

See merge request gitlab-org/gitlab-ce!18556

Resolve "Broken master with `static_analysis` and `karma` being broken"

Closes #45725

See merge request gitlab-org/gitlab-ce!18569

Broken link fix

See merge request gitlab-org/gitlab-ce!18564

Add copy_metadata quick action

Closes #38450

See merge request gitlab-org/gitlab-ce!18497

Fix errors on pushing/editing files on empty repositories

Closes #44618 and #42583

See merge request gitlab-org/gitlab-ce!18462

Add documentation for externally hosted LFS objects

See merge request gitlab-org/gitlab-ce!18508

Resolve "Add some way to mock and spy on default ES modules"

Closes #30998

See merge request gitlab-org/gitlab-ce!18116

Fix unassign slash command preview

See merge request gitlab-org/gitlab-ce!18447

Merge branch '43111-controller-projects-mergerequestscontroller-index-executes-more-than-100-sql-queries' into 'master'

Resolve "Controller Projects::MergeRequestsController#index executes more than 100 SQL queries"

Closes #43111

See merge request gitlab-org/gitlab-ce!18561

Show Runner's description on job's page

See merge request gitlab-org/gitlab-ce!17321

Hide the push to master instructions for users that are not allowed to
do that.

Also hide buttons that would direct them to commit directly in master

API can be used by project owners to disable LFS object verification
that will block pushes that contain LFS pointers but no the objects.

Introduce new ProjectCiCdSettings model with group_runners_enabled

See merge request gitlab-org/gitlab-ce!18144

Improve documentation of SSRF protection

Closes #45057

See merge request gitlab-org/gitlab-ce!18532

Refactor OmniauthCallbacksController to remove duplication

Closes #26559

See merge request gitlab-org/gitlab-ce!16694

Warning when restore fails when data-dir is a moint point

Closes #19309

See merge request gitlab-org/gitlab-ce!18533

Added fuzzy file finder to web IDE

Closes #44841

See merge request gitlab-org/gitlab-ce!18323

Bump lograge to 0.10.0 and remove monkey patch

See merge request gitlab-org/gitlab-ce!18551

Replace find file project spinach tests with RSpec

See merge request gitlab-org/gitlab-ce!18528