Add docs for resolve conflicts editor

See merge request !8748

[ci skip]

Merge the two 2FA docs into one

See merge request !8747

[ci skip]

Add due dates docs

See merge request !8744

[ci skip]

Allows to search within project by commit's hash #24833

Closes #24833

See merge request !8028

Small update to the Mattermost API

See merge request !8712

Grapify all endpoints of the deploy keys API

See merge request !8721

Fix hash of ruby in update documentation

See merge request !8735

Backport EE changes on approvals reset for closed MRs

See merge request !8559

Add docs for confidential issues

Closes #14397

See merge request !8741

[ci skip]

See !8028 and #24833

Was proposed in #24833

Requeue projects pending deletion

See merge request !8438

[ci skip]

These changes make it possible to wrap multiple API requests in one
session.

There have been several bugs in the project deletion service and worker.
Resulting in projects stuck in pending delete state, which limits users
to create projects with the same name, keeps stale records in the
database, and all kinds of other trouble.

This post deployment migration requeues all these projects for deletion,
in the hope that most of these could be removed by the updated code.

Disable automatic login feature when clicking on email confirmation links

See merge request !7472

Resolve "Comment/Description textarea shows a blue border on the left"

Closes #27066

See merge request !8720

Pick security fixes from 8.16.1 et al into master

Closes #26813, #26249, #26259, #26243, #26242

See merge request !8724

Rename endboss -> maintainer, miniboss -> reviewer

See merge request !8719

Handle unsubscribe notification via email

Closes #22619

See merge request !6597

Allow creating protected branches when user can merge to such branch

Closes #22638

See merge request !8458

Remove rogue scrollbars from some issue comments

Closes #25989

See merge request !8652

Allow issue filter submission using mouse only

See merge request !8681

Upgrade OmniAuth Ruby gem to 1.3.2

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/26813

See merge request !2056

Prevent users from creating notes on resources they can't access

See https://dev.gitlab.org/gitlab/gitlabhq/merge_requests/2054

Ensure that only privileged users can access merge requests in the API

See merge request !2053

Fix export files not removed when a user takes over a namespace

See merge request !2051

Fix users being able to delete instance public deployment keys

See merge request !2049