Ensure the 'fixed layout' preference is honored whenever possible

## What does this MR do?

Currently, when viewing any Merge Request the user's fixed-layout preference is overridden if they have set "Side-by-Side" view as their preference when viewing diffs.  This makes sense if they are currently viewing a diff, but this is confusing when their layout preference is overridden while they are on another tab (i.e. "Discussion" or "Builds").

This MR moves all responsibility for overriding the fixed layout from the Ruby page layout helper into frontend JavaScript where it is only applied when needed.

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

Check that nothing broke for users which have their layout preference set to "Fluid" as well as those which have it set to "Fixed".  I've already done this but double checking is always good idea 😄.

## Screenshots (if relevant)

![side-by-side-toggle-fixed](/uploads/033dc73e70b73da5692b75606733c938/side-by-side-toggle-fixed.gif)

## Does this MR meet the acceptance criteria?

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

## What are the relevant issue numbers?

Closes #22343 

## Other Notes

As @lbennett noted in #22343, this is something of a band-aid.  It fixed most of the issue, but we still need to have a discussion about whether or not is acceptable to override user layout preferences for "Side-by-Side" views in general.  At least this MR limits the scope of this behavior to a single tab within an MR or merge conflict page.

See merge request !6422

Fix bug when trying to cache closed issues from external issue trackers

fixes #22446

See merge request !6619

Upgrade acts-as-taggable-on from 3.5.0 to 4.0.0.

## What does this MR do?

Upgrades the acts-as-taggable-on gem from 3.5.0 to 4.0.0.

Changelog: https://github.com/mbleigh/acts-as-taggable-on/blob/master/CHANGELOG.md#400--2016-08-08

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

That this works without the migrations, I don't believe the upgrade from 3.5.0 to 4.0.0 requires any migrations since [UPGRADING.md hasn't been updated since 3.5.0 was released](https://github.com/mbleigh/acts-as-taggable-on/blob/master/UPGRADING.md). It's kind of unclear, unfortunately.

## What are the relevant issue numbers?

Fixes #22082. Working toward Rails 5: #14286.

cc: @dzaporozhets

See merge request !6660

Simplify Mentionable concern instance methods

## What does this MR do?

Simplify arguments received by the instance methods on the concern so in the closer future will be easy to understand and change

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

## Why was this MR needed?

## Screenshots (if relevant)

## 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 [merge request performance guides](http://docs.gitlab.com/ce/development/merge_request_performance_guidelines.html)
- [ ] 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)

## What are the relevant issue numbers?

See merge request !6596

Improve `Members::DestroyService`

Part of #21979.

See merge request !6267

Append issue template to existing description

## What does this MR do?

When selecting an issue template after entering a description, append the template and leave the original content intact.

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

Not that I'm aware of.

## Why was this MR needed?

The issue template shouldn't override the issue content without warning.

## Screenshots

![](https://i.imgur.com/E16X2tc.gif)

## Does this MR meet the acceptance criteria?

- [x] [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
  - [x] Added for this feature/bug
  - [x] All builds are passing
- [x] Conform by the [merge request performance guides](http://docs.gitlab.com/ce/development/merge_request_performance_guidelines.html)
- [x] Conform by the [style guides](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CONTRIBUTING.md#style-guides)
- [x] Branch has no merge conflicts with `master`
- [x] [Squashed related commits together](https://git-scm.com/book/en/Git-Tools-Rewriting-History#Squashing-Commits)

## What are the relevant issue numbers?

https://gitlab.com/gitlab-org/gitlab-ce/issues/21733

See merge request !6149

Todo issue due date

## What does this MR do?

Adds the text 'Due today' or 'Due [DATE]' next to issues in todos.
This does not add anyway to filter by due date - little steps.

## What are the relevant issue numbers?

#18218

See merge request !6351

GrapeDSL for Namespace endpoint

No changelog item as it doesn't change behaviour

Cherry-picked from !6330

See merge request !6632

Fix issues importing services via Import/Export

Prevents errors when initialising services that do not have any properties set yet - case that could happen when importing projects.

Fixes https://gitlab.com/gitlab-org/gitlab-ce/issues/22891

See merge request !6667

We remove some arguments that are rarely used or 
used just to simplify setups on specs.

Modified Mentionable#create_new_cross_references method 
we don’t need to calculate previous references to avoid the 
duplication because we do that at database level when 
creating references extracted from the current entity state.

MergeRequests won’t create cross_references for commits that are included so we change a spec to use a different merge request to make references to commits to other branches

Add Container Registry on/off status to admin area

## What are the relevant issue numbers?

Closes #22805

See merge request !6638

Remove SCSS rules for short hex chars.

## What does this MR do?
Remove CSS hex shorthands linter
## Are there points in the code the reviewer needs to double check?
That I did it right. 
## Why was this MR needed?
To remove SCSS linter for hex shorthands
## Screenshots (if relevant)

## 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 [merge request performance guides](http://docs.gitlab.com/ce/development/merge_request_performance_guidelines.html)
- [ ] 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)

## What are the relevant issue numbers?
Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/22920

cc @connorshea

See merge request !6663

Changed mr widget build status to pipeline status

## What does this MR do?

Changed mr widget build status to pipeline status with pipeline id, with a link to the pipeline.

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

Do we want the link to the pipeline?

/cc @dimitrieh 

## Screenshots (if relevant)

![Screen_Shot_2016-09-14_at_02.42.23](/uploads/94a860361ab70eccf966e519764c6ec5/Screen_Shot_2016-09-14_at_02.42.23.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 [merge request performance guides](http://docs.gitlab.com/ce/development/merge_request_performance_guidelines.html)
- [ ] 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)

## What are the relevant issue numbers?

Closes #22006

See merge request !6335

Changelog: https://github.com/mbleigh/acts-as-taggable-on/blob/master/CHANGELOG.md#400--2016-08-08

Fix tooltip text when Copy to cliboard is clicked

## What does this MR do?

Fixes #22022 to change tooltip text to "Copied!" when the "Copy to clipboard" button is clicked.

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

Line 29 in app/assets/javascripts/copy_to_clipboard.js

## Why was this MR needed?

There was a regression that prevents tooltip change on button click for Copy to clipboard.

## Does this MR meet the acceptance criteria?

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

## What are the relevant issue numbers?

Closes #22022

See merge request !6294

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

See https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/6149#note_14830172

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/21733

Add two newlines before the template if the existing description isn't
empty. This makes it easier to see where the template begins.

Don't append the template when "Reset template" is selected, of course.

Don't append template if it equals the existing description. This makes
it so that selecting a template twice doesn't duplicate it.

Enable Lint/StringConversionInInterpolation cop and autocorrect offenses



See merge request !6654

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

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

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

Display the on/off icon under the "Features" section of the admin area
for the Container Registry.

Closes !22805

Changed Slack service user referencing from full name to username

Closes #22737

See merge request !6624

Add configurable email subject suffix

## Why was this MR needed?

I noticed that there is a commit 44ab156e 3 years ago which removes email subject prefix

actually we do need an special part of the email subject which makes the email subject easy to identify

we just need to make it configurable rather than remove it.

See merge request !6172

Log sidekiq arguments as json

Logging the sidekiq job arguments as a ruby literal structure 
is akward. Specially when parsing the logs.

JSON is a standar format.



See merge request !3735

Resolve "Task List Checkbox Alignment"

## What does this MR do?

Replace the unmaintained `task_list` gem with the `deckar01-task_list` fork

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

 - I had to pin some dependencies in the fork to support `ruby < 2.2`, which added new version restrictions for 2 existing modules.
 - I triggered a build after I removed the patch to show the test passed with the new gem, then I removed the test, because this behavior is tested in the gem's repo now.

## Why was this MR needed?

 - The `task_list` patch was added with a comment that said it should be removed when merged upstream, but the repo got archived, so an upstream patch requires a fork.
 - #22470 can't be patched without warnings due to the way `task_list` uses Ruby constants.
 - There are additional outstanding `task_list` bugs that can be fixed once we switch to a fork.

## What are the relevant issue numbers?

 - #22466 
 - #22470
 - !6487

See merge request !6625

GrapeDSL for Award Emoji endpoints

Cherry-picked from !6330

See merge request !6629

Enable Import/Export for non-admin users

Fixes https://gitlab.com/gitlab-org/gitlab-ce/issues/21315

Related https://gitlab.com/gitlab-org/gitlab-ce/issues/20857 and https://gitlab.com/gitlab-org/gitlab-ce/issues/20821/

See merge request !6080

Use custom Ruby images to test builds

It allows us to remove redundant steps of installing required dependencies for every build.


See merge request !4506

Better empty state for Groups view.

Implemented @hazelyang's [awesome design](https://gitlab.com/gitlab-org/gitlab-ce/uploads/9141470ed121f137a4074ae4e12c449c/groups-empty.png) for empty group views.

Fixes #20829 


### Design
![https://gitlab.com/gitlab-org/gitlab-ce/uploads/9141470ed121f137a4074ae4e12c449c/groups-empty.png](https://gitlab.com/gitlab-org/gitlab-ce/uploads/9141470ed121f137a4074ae4e12c449c/groups-empty.png)


### Screenshots
![Screen_Shot_2016-09-28_at_13.43.35](/uploads/e2ab668a412596205deb67c97af78a1d/Screen_Shot_2016-09-28_at_13.43.35.png)

![Screen_Shot_2016-09-28_at_13.44.54](/uploads/c4301166f353f0ee198aecdc46cdfe66/Screen_Shot_2016-09-28_at_13.44.54.png)

![Screen_Shot_2016-09-28_at_13.46.10](/uploads/92024e866871969ec7a28db4b8e87220/Screen_Shot_2016-09-28_at_13.46.10.png)

![Screen_Shot_2016-09-28_at_13.46.20](/uploads/f1b515c7aa09d06e80a419d98ff76fd6/Screen_Shot_2016-09-28_at_13.46.20.png)

![Screen_Shot_2016-09-28_at_13.46.34](/uploads/76cdd5f0e9d3c59d017df26172f7dd4d/Screen_Shot_2016-09-28_at_13.46.34.png)

See merge request !6566

Convert "SSH Keys" Spinach features to RSpec

See merge request !6639