DRY code + fix rubocop

Add more test cases

Append to changelog

DRY changes list

find_url service for merge_requests

use GET for getting merge request links

remove files

rename to get_url_service

reduce loop

add test case for cross project

refactor tiny thing

update changelog

Remove Grack::Auth: part 2 (LFS)

Deprecate Grack::Auth and handle LFS in Rails controllers under the Project namespace.

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/14501

See merge request !5369

Refactor pipeline creation service

## What does this MR do?
This refactors GitLab CI build processing: all builds for pipeline are pre-created when a pipeline object is created. 
The builds are created with a new introduced status `created`.
The builds are then automatically promoted to `pending` when a previous stage do succeed.
This significantly simplifies pipeline processing code solving a lot of problems of lazily initialisation of previous approach (builds were created on-demand).

## Why was this MR needed?
The previous mechanism had a lot of flows (shown in related issues) in how it work, but also in code design. Removing cross model-service-library dependencies.

The current approach moves a build creation to single place `CreatePipelineService` and removes a dynamic dependency on `config_processor` significantly simplifying a build creation and pipeline processing. Pipeline processing is implemented in `ProcessPipelineService`.

This also allows to easily extend GitLab with Manual Actions which is part of 8.10 direction issue.

## Migration problem
~~This MR removes the a on-demand creation of builds in pipelines.
 Pipelines that are running and are in mid-stage (some stages started, but not all) will not be fully evaluated after application restart. 
This happens, because the code responsible for on-demand creation is removed. 
There's no easy way to migrate existing pipelines, other than doing offline migration and putting pipeline processing in migration code (which seems to be a really bad idea).~~

To support old pipelines I added a lazy initialization of builds if none is found.

## What are the relevant issue numbers?
Fixes: https://gitlab.com/gitlab-org/gitlab-ce/issues/12839
Solves: https://gitlab.com/gitlab-org/gitlab-ce/issues/18644 https://gitlab.com/gitlab-org/gitlab-ci-multi-runner/issues/289
Allows to easily implement: https://gitlab.com/gitlab-org/gitlab-ce/issues/17010

## 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
  - [ ] 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)
- [ ] [Squashed related commits together](https://git-scm.com/book/en/Git-Tools-Rewriting-History#Squashing-Commits)


See merge request !5295

This change simplifies a Pipeline processing by introducing a special new status: created.
This status is used for all builds that are created for a pipeline.
We are then processing next stages and queueing some of the builds (created -> pending) or skipping them (created -> skipped).
This makes it possible to simplify and solve a few ordering problems with how previously builds were scheduled.
This also allows us to visualise a full pipeline (with created builds).

This also removes an after_touch used for updating a pipeline state parameters.
Right now in various places we explicitly call a reload_status! on pipeline to force it to be updated and saved.

Fix front-end for branches that happen to contain urlencoding escape characters (e.g. %)

_Originally opened at !3574 by @ewiltshi._

- - -

Adding a branch with a name like "foo%20bar" (via command-line) and setting it to the project's default branch causes the project "show" page to 404 for that project. "assign_ref_vars" unescapes the branch name ("foo%20bar" ==> "foo bar"), making GitLab look for a non-existent branch.
This MR adds logic to skip the URL unescaping step in "assign_ref_vars".

Fixes #10772, #14992, #15304.

## Does this MR meet the acceptance criteria?

- [x] [CHANGELOG](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CHANGELOG) entry added
- 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 !5770

Use `File::exist?` instead of `File::exists?`

Each `File::exists?` replaced to `File::exist?`.

Since version ruby-2.2.0, method `File::exists?` is deprecated.

See merge request !5747

Add group members API endpoints to request access and approve requests

## What does this MR do?

Add group members API endpoints to request access and approve requests.

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

I chose to factorize the group/project members API as well as the new group/project access requests API.

I initially also created new services to centralize the permission checks related to actions on members, but this was out of scope and this MR is already quite big so I opened a temp MR at !5566 based on this one.

## Why was this MR needed?

To finish the "request access" feature.

## What are the relevant issue numbers?

Closes #18583.

## 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 !4833

Fixing scope issue in GitAccess.

This MR fixes a scoping issue around the GitAccessStatus.new call - it needs to be scoped to the Gitlab otherwise it can end up being confused with the GitAccessStatus class in gitlab-shell, which has a 3-element constructor.

Although not strictly necessary for community GitLab, it is more correct, and fixes an issue we (Perforce) found due to our engine overrides.

This change should have any affect on community GitLab.

See merge request !5483

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

Since version ruby-2.2.0, method `File::exists?` is deprecated.