Add internal API to recovery 2FA

## What does this MR do?

Add an internal API to make SSH 2FA recovery possible. Related to gitlab-org/gitlab-shell!74

See merge request !5510

Add Sentry logging to API calls

## What does this MR do?

This MR adds support for Sentry logging in the API.

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

Since the `Grape::Middleware` doesn't have a `params` method, I had to define one using the Rack Request.

## Why was this MR needed?

We are missing a lot of useful errors in the API causing git push/pull errors

## What are the relevant issue numbers?

#21043

See merge request !5882

changes from using size to count and caching it to get the number of members in a group

- [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 [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)
Closes #20909

See merge request !5935

Does not halt the GitHub import process when an error occurs

## What are the relevant issue numbers?

Fixes #20385 

https://gitlab.com/gitlab-org/gitlab-ce/issues/20149

## Does this MR meet the acceptance criteria?

- [x] [CHANGELOG](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CHANGELOG) entry added
- Tests
  - [x] 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)

See merge request !5763

Restore get_id in ExtractsPath

fixes #21334

`Addressable::URI.normalize_component()` around `get_id` which was introduced by 68cea38e and removed in !5878 is still intentionally omitted. Using `normalize_component()` instead of `unescape()` left `%` as is but still broke e.g. spaces (which were replaced by `%20`).

See merge request !5974

Use gitlab-workhorse 0.7.11

Versions 0.7.9 and 0.7.10 crash on previously valid 'authBackend'
settings.

I don't know how many people are affected by this, 'normal' Omnibus
installations are not. (If they were gitlab.com would have stopped
working :) ). Still this is something we should not ship.
Unfortunately 8-11-stable uses 0.7.10 (but 8.11.0 does not). So I
think we need to put this in the next 8.11 patch release.

See merge request !5983

expose 'only_allow_merge_if_build_succeeds' project setting in the API

## What does this MR do?
Adds the 'only_allow_merge_if_build_succeeds' project setting in the API.

## Are there points in the code the reviewer needs to double check?
No, but maybe this code is not enough for ACLs or the like.

## Why was this MR needed?
Because that's a very useful setting to change via automation (through the API)

## What are the relevant issue numbers?

Closes #21085, closes https://gitlab.com/gitlab-org/gitlab-ce/issues/20088.

## Screenshots (if relevant)

## 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 [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)

See merge request !5930

api: expose web_url for project entities

## What does this MR do?

Adds a `web_url` field to project snippet, issues, and merge request API returned objects.

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

Tests. Are they sufficient? (I'm working on getting them to pass.)

## Why was this MR needed?

Creating the URL for an MR or issue from the MR is tedious in API libraries; it's easy for Gitlab to just provide it.

## What are the relevant issue numbers?

N/A

## Screenshots (if relevant)

N/A

## 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 [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)

See merge request !5631

Closes #21043

Update merge_requests.md with a simpler way to check out a merge request

## What does this MR do?

This MR updates `merge_requests.md` with a simpler way to check out a merge request 

The previous way was put under the "By modifying `.git/config` for a given repository" section. The disadvantage of the old way is that one has to modify `.git/config` for each repository that one uses. The new way was put under the "By adding a git alias" section. One has to create this git alias once, and then it will work from any repository, without having to modify `.git/config` over and over again.

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

One should double check that the link provided by the "Check out branch" button in a MR, i.e. https://gitlab.com/gitlab-org/gitlab-ce/blob/master/doc/workflow/merge_requests.md#checkout-merge-requests-locally, still works. I think it will, since I didn't modify the "Checkout merge requests locally" section name.

## Why was this MR needed?

This MR was needed because the old way of checking out a merge request locally requires to modify `.git/config` in all repositories that one has on a computer, which is a tedious task. The new way just requires adding a simple git alias, once. And the `git mr` command then works for all repositories.

## What are the relevant issue numbers?

I haven't created an issue for this.

## Screenshots (if relevant)

N/A

## 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)
- [ ] API support added (N/A)
- Tests
  - [ ] Added for this feature/bug (N/A)
  - [x] 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)

See merge request !5944

Api project hook wiki page events

## What does this MR do?

Updates project hook API for wiki page events. Also updates docs and tests for forgotten hook fields.

See merge request !5969

last_push_event widget considers fork events on the main project

Push events on the fork of the current project are considered to be shown besides the push events on the current project. Before we just consider fork events if exists a fork so we miss current project events if the current user has a fork.

Closes #20254

See merge request !5978

Issue created at docs

## What does this MR do?

Clarifies `created_at` for creating issues via the API.

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

No.

## Why was this MR needed?

Docs were unclear.

## What are the relevant issue numbers?

Closes #18458 and closes #19863.

## Screenshots (if relevant)

N/A

## Does this MR meet the acceptance criteria?

- [x] [Documentation created/updated](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/doc/development/doc_styleguide.md)
- [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)

See merge request !5967

Add tests coverage report badge to README

## What does this MR do?

This MR adds tests coverage badge to project's README.

The job it reads coverage value from is `coverage`, and it is configured in out CI test suite to calculate compound coverage from all test jobs running in parallel.

This will pick the latest successful pipeline to get `coverage` job and coverage value.

For now, this will report test coverage only for backend test suite (Ruby).

See merge request !5925

Update Ruby version to 2.3 in Requirements

According to the [GitLab 8.11 release notes](https://about.gitlab.com/2016/08/22/gitlab-8-11-released/), Ruby 2.3 is now supported and recommended. Update the documentation accordingly.

See merge request !5965

This allows web hooks to have a URL back to entities without having to
generate it themselves.

See also #19863.

Fixes #18458.

Versions 0.7.9 and 0.7.10 crash on previously valid 'authBackend'
settings.

members page

Disable commenting on unrelatable diff line

## What does this MR do?

Fixes a bug where users can comment on diff lines that can't be commented on and attached to.

This is the case for unfolded lines and lines that appear as snippets in the discussion tab.

**!5864 should be merged before this MR.**

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

😕 

## Why was this MR needed?

Comments were getting lost on the discussion feed, unable to find their related diff.

## What are the relevant issue numbers?

Closes #20633.

## Screenshots (if relevant)

![diffs-comment-fix](/uploads/f902b687fda75492e38397f9705283e0/diffs-comment-fix.mp4)

## 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 !5681

Fix file links on project page Files view

## What does this MR do?

Fix the project show page when the default view is set to Files so that the links work.

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

I can't figure out what caused this to break 😕 

## What are the relevant issue numbers?

Closes https://gitlab.com/gitlab-com/support-forum/issues/959.

## 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) (N/A)
- [x] API support added (N/A)
- Tests
  - [x] Added for this feature/bug
  - [ ] 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)

See merge request !5933

Now the alias should be used as:

    git mr upstream 5

To check out a MR number 5 from the upstream remote, into a `mr-upstream-5`
local branch.

Also clarify that the `5` in the merge request is the number shown in GitLab.

Fix Spinach branches spec

I broke master by adding a branch to gitlab-test for https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/5961, which put the branch in this scenario off the first page 😆 

See merge request !5964