Remove unnecessary sentences for return codes in the API documentation

Closes #24534

See merge request !7511

Slash commands improvements

See merge request !7638

Resolve "Reduce queries in API::Helpers#find_project"

See merge request !7714

For example, now we support `/gitlab issue show #1`. Where the # used
to trip the regex.

Improve how we could cancel pipelines:

Improve how we could cancel pipelines:

* Introduce `HasStatus.cancelable` which we might be able to cancel
* Cancel and check upon `cancelable`
* Also cancel on `CommitStatus` rather than just `Ci::Build`

Fixes #23635

Fixes #17845

See merge request !7508

Allow GFM autocomplete to be trigger without the preceding space

## What does this MR do?

Gives the ability to GFM autocomplete to be trigger even if there is no preceding space.

I've taken the regex from the at.js plugin & tweaked it to allow the leading character to be a special character.

## What are the relevant issue numbers?

Closes #19975 

## Screenshots (if relevant)

![Screen_Shot_2016-07-21_at_14.41.34](/uploads/19684ba286baeedb754e7457945480a8/Screen_Shot_2016-07-21_at_14.41.34.png)![Screen_Shot_2016-07-21_at_14.41.40](/uploads/a77349bce599ae93b4bcddd355087f5c/Screen_Shot_2016-07-21_at_14.41.40.png)![Screen_Shot_2016-07-21_at_14.41.46](/uploads/c35df17b678b24b73c94b181f0784188/Screen_Shot_2016-07-21_at_14.41.46.png)

See merge request !5395

Fix title case to sentence case in "Add Todo"

## What does this MR do?
Implements sentence case for `Add Todo`

## Are there points in the code the reviewer needs to double check?
I changed the images used in the file `doc/workflow/todos.md` to show the new look.

## Why was this MR needed?
#24748 

## Screenshots (if relevant)
Before
![Screen_Shot_2016-11-21_at_12.03.21_PM](/uploads/225abe2901aacccea697596853bdc52c/Screen_Shot_2016-11-21_at_12.03.21_PM.png)
![Screen_Shot_2016-11-21_at_11.58.17_AM](/uploads/3a5997eb6bb037f1c581d9925fa288ce/Screen_Shot_2016-11-21_at_11.58.17_AM.png)

After
![Screen_Shot_2016-11-21_at_12.03.38_PM](/uploads/3be4d58e5adaa10fab759f8726a4d257/Screen_Shot_2016-11-21_at_12.03.38_PM.png)
![Screen_Shot_2016-11-21_at_11.58.37_AM](/uploads/016cdb32cb1e87e9e3cfd89309b53a4a/Screen_Shot_2016-11-21_at_11.58.37_AM.png)


## Does this MR meet the acceptance criteria?

- [X] [Changelog entry](https://docs.gitlab.com/ce/development/changelog.html) added
- [X] [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)
- [X] Branch has no merge conflicts with `master` (if it does - 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?
#24748

See merge request !7724

Fix bad selection on dropdown menu for tags filter

Fixes #24958

See merge request !7750

Rephrase some system notes to be compatible with new system note style

See merge request !7692

Make test suite deterministic when storage is involved

## What does this MR do?

This MR fixes our RSpec test harness because one test example could affect subsequent examples if objects created with `let` had associated files stored in `tmp/tests`.

We store files using CarrierWave, but we also have some custom storage rules for CI builds. Some time ago we introduced MR that purged CarrierWave uploads after each run of entire test suite https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/3435, but this is not enough, as we should isolate each test example to be able to rely on deterministic test suite.

Not cleaning uploads between each test example run, makes it impossible to know if preconditions are correct before test example starts to run, therefore it makes test examples, that use storage, unreliable. This MR is an attempt to improve that.  

## What are the relevant issue numbers?

Closes #24808

See merge request !7695

Update grape-entity to 0.6.0

See merge request !7491

resolves updated and resolved status is not showing

## What does this MR do?
This MR fixes #24780 

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

## Why was this MR needed?
This MRs removes some important information as par suggested design in #19797. it restores that information

## Screenshots (if relevant)
**Before:**
![before](/uploads/a93091e783de3e550a07ddbc1fa8085a/before.png)
**After:**
![after](/uploads/ceb7f64a6f20155abcf6ea49d4b8059e/after.png)

## Does this MR meet the acceptance criteria?

- [ ] [Changelog entry](https://docs.gitlab.com/ce/development/changelog.html) 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
  - [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 it does - 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 #24780

See merge request !7655

Fixed resolved discussion timeago not rendering

## What does this MR do?

Initialises the timeago element when a discussion is updated or resolved.

## Screenshots (if relevant)

![Screen_Shot_2016-11-22_at_11.49.22](/uploads/02900cc4de019ac33cd4d59d586629aa/Screen_Shot_2016-11-22_at_11.49.22.png)

## What are the relevant issue numbers?

Closes #24787

See merge request !7656

Fixed commit time not rendering after initial page load

## What does this MR do?

Inits the timeago for commits when infinite scrolling which fixes the issue of the timeago not rendering correctly when scrolling down.

## What are the relevant issue numbers?

Closes #24862

See merge request !7704

Properly escape username validation error

## What does this MR do?

Prevents the double-escaping of the username validation error when attempting to change one's username using an invalid character.

Go to [/profile/account](https://gitlab.com/profile/account) and attempt to add an invalid character like `@` or `#` to your username to trigger this message.

## Screenshots (if relevant)

#### Before:
![user-name-change](/uploads/8e509ca8a22e40fd51c3c1919e9c6871/user-name-change.png)

#### After:
![Screen_Shot_2016-11-23_at_5.23.52_PM](/uploads/3e868128724e6af07d1193494ec25941/Screen_Shot_2016-11-23_at_5.23.52_PM.png)

## Does this MR meet the acceptance criteria?

- [ ] ~~[Changelog entry](https://docs.gitlab.com/ce/development/changelog.html) 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
- [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 it does - 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 #23813

See merge request !7725

Fixed issue boards scrolling with a lot of lists & issues

## What does this MR do?

When an issue board has a lot of lists & each list has a lot of issues scrolling can be tricky. This changes that by making the element that scrolls the `board-list` div. This is ok because sorting inside each list isn't possible, it will need re-thinking when sorting is possible but this fixes the bug for now.

See merge request !7748

Stop supporting Google Cloud and Azure as backup strategies

## What does this MR do?

It removes support for Azure and Google Cloud as backup strategies (via Fog).

Motivation behind this decision can be found in !4928, !6713 but basically they require a lot of gems that are unrelated to the backup use-case.

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

Am I missing any other location where we'd use these gems?

See merge request !7739

Fixed issue boards issue sorting when dragging issue into list

## What does this MR do?

Currently it just appends the new issue to the end of list & then sorts by priority which can cause some strange effects. For example if you drag the issue to the top of the list & then vue re-renders, the issue actually goes to the bottom.

This changes that by adding the issue at the specific index.

## Screenshots (if relevant)

![boards-sorting](/uploads/9aa4a0cb5e0be79e7d24ab2b6abb0bbb/boards-sorting.gif)

See merge request !7734

When a board has a lot of lists & issues scrolling stops the user from moving the issue to the lsat list (or any list not on screen). This changes that by making the scrollable element the board-list element. This will need re-thinking when sorting in lists is possible.

Pick valid event objects for the events list

## What does this MR do?
Fixes JS error when loading events with possible `null` objects

## What are the relevant issue numbers?
Closes #24836

See merge request !7689

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

You can only assign default_branch when editing a project

Related to https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/7726

See merge request !7741

You can only assign default_branch when editing a project or when creating a project for a specified user [ci skip]

You can only assign default_branch when editing a project [ci skip]

changes environment.last_deployment to a try expression so it does not fail if e…

## What does this MR do?

Fixes the call on `environment.last_deployment` to not break when `environment`is not yet set.

## Does this MR meet the acceptance criteria?

- [x] [Changelog entry](https://docs.gitlab.com/ce/development/changelog.html) 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 it does - 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 #24779

See merge request !7671

Don't convert data which already is the target type

With Grape's DSL we already enforce data types. We don't need to explicitly convert to string if there is already one.

See merge request !7740

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

Move admin spam spinach test to RSpec

See merge request !7708

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

Merge branch '24908-install-instructions-seem-to-have-two-database-steps-out-of-order' into 'master'

Fix documentation to create the `pg_trm` extension before creating the DB

Closes #24908

See merge request !7735

The amount of gems required is quite high compared to the usefulness
of the features.

Related to !4928, !6713
Signed-off-by: Rémy Coutable <remy@rymai.me>

Add missing documentation.

## What does this MR do?

Add documentation to Build events on webhooks

See merge request !7717

Add default_branch attr to Project API payload in docs.

See merge request !7726

Document that we always use `do...end` for `before` in RSpec

[ci skip]

See merge request !7697

Add missing JIRA file that redirects to the new location

See merge request !7736