Resolve "Option to disallow author to approve merge request"

This prevents an MR from being approved by the author of the MR. The
author won't see the approve MR button, and if they try via the internal
or public API, it will fail.

Closes #388.

See merge request !455

Port of gitlab-org/gitlab-ce!3798 to EE

Allow users to request access to projects and groups

See merge request gitlab-org/gitlab-ce!3798

/cc @vsizov 

See merge request !460

Distribute RepositoryUpdateMirror jobs with exclusive lease

See merge request !462

Signed-off-by: Rémy Coutable <remy@rymai.me>

UpdateAllMirror jobs try to update each mirror status and later
add a job to update the mirror. We’ll distribute at what time 
that job will be executed trying to avoid locks updating project 
import_status column

Signed-off-by: Rémy Coutable <remy@rymai.me>

[EE] Improve gitlab:env:info

Added additional information (which we already display in `Admin > Dashboard`) to help troubleshooting issues in Geo (#76).

See merge request !459

Update kerberos integration guide based on feedback

Updates based on user feedback. 

cc// @axil 

ZD: https://gitlab.zendesk.com/agent/tickets/26695

See merge request !456

Remove icon from Contribution Analytics navigation
Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

cc @vsizov @jschatz1 

See merge request !461

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

Previously, this would pick the least-frequent contributors to the
changed files, rather than the most frequent.

Allow users to request access to projects and groups

See merge request gitlab-org/gitlab-ce!3798
Signed-off-by: Rémy Coutable <remy@rymai.me>

Refactor license doc

- Add section on missing license
- Move images in a separate directory

See merge request !457

[ci skip]

- Add section on missing license
- Move images in a separate directory

[ci skip]

Geo: Improve UI for users in a Geo node

This implements visual hints to help user diagnose Geo (#76) installations, and help guide users that are in a secondary node to understand that they are in a read-only instance.

Fixes gitlab-org/gitlab-ee#640

# First login flash message
![first-login_notice](/uploads/51507c12eb8f4ec29a9e58dbc4c1b716/first-login_notice.png)

# Admin screen - Dashboard information
![admin-screen](/uploads/ee1b3b50a013cd5195c7e2047497d387/admin-screen.png)

# Link to primary node 
![link_to_primary_node](/uploads/6061d64690cda83f49145f9643d0e0bd/link_to_primary_node.png)

See merge request !451

CE upstream



See merge request !452

Fixed first login flash notice after login from Geo primary

Signed-off-by: Rémy Coutable <remy@rymai.me>

Signed-off-by: Rémy Coutable <remy@rymai.me>

Signed-off-by: Rémy Coutable <remy@rymai.me>

Merge branch '18446-when-this-merge-request-is-accepted-this-issue-will-be-closed-automatically-rendered-twice' into 'master'

Resolve ""When this merge request is accepted, this issue will be closed automatically" rendered twice"

## What does this MR do?

1. Only show the above text when there is an MR that will close the issue, and even then, only show it once.
2. Apply 98f147e84d2bd8f2278452ac0852118452c76d4a to a bunch of other places that need it.

## Are there points in the code the reviewer needs to double check?

¯\_(ツ)_/¯

## Why was this MR needed?

Some pages were broken.

## What are the relevant issue numbers?

Fixes #18446.

## Screenshots (if relevant)

Before:
![image](/uploads/23cfaf95b7c798f22963ff67f78a803b/image.png)

After:
![image](/uploads/ca9c538069ba52e53858c69387738521/image.png)

## Does this MR meet the acceptance criteria?

- [ ] [CHANGELOG](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CHANGELOG) entry added
- [ ] [Documentation created/updated](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/doc/development/doc_styleguide.md)
- [ ] API support added
- [ ] Tests
  - [ ] Added for this feature/bug
  - [ ] All builds are passing
- [ ] Conform by the [style guides](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CONTRIBUTING.md#style-guides)
- [ ] Branch has no merge conflicts with `master` (if you do - rebase it please)
- [ ] [Squashed related commits together](https://git-scm.com/book/en/Git-Tools-Rewriting-History#Squashing-Commits)

See merge request !4594

Improve SVG sanitizer to handle namespaced attributes

* Small refactor in the SVG sanitizer
* Enable already whitelisted namespaced attributes to be allowed
* Disable `xlink:href`to reference any external resource

Fixes #18100 

See merge request !4427