Merge branch 'gokmengoksel/gitlab-ce-koding' into 'master'

Koding Integration

## What does this MR do?

Will provide Koding integration with GitLab services. Forked from !4914.

## Are there points in the code the reviewer needs to double check?
I've introduced new layouts which might not be necessary, first time contributor. 

## Why was this MR needed?
We're planning to ship Koding with GitLab.

## What are the relevant issue numbers?
#12759 #14698 

## Screenshots (if relevant)

### Screencasts

http://recordit.co/BDMbhwgxPD
http://recordit.co/By0qiz1ClC

### Enable Koding in Application Settings

![image](/uploads/73a69421105c03aa2b0b47e2617d3fbc/image.png)

### Koding Dashboard
![image](/uploads/6c7dda34792280c0e4791e36af4eba11/image.png)

### Set up Koding Stack
1 - ![image](/uploads/d5c2b93f8e61b5cbffdb06f0267d485f/image.png)
2 - ![image](/uploads/44d9a9b574b8ac0c5eb553fb9653d5da/image.png)

### Run on Koding on Project Page

![image](/uploads/7d2b46221009074ffff75d66d5a1a555/image.png)

### Run in IDE on Merge Requests
![image](/uploads/65eed90c34c34b5fe7ad29ef9c717640/image.png)

## 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] 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 !5909

2 files changed, 17 insertions, 0 deletions

diff --git a/app/controllers/admin/application_settings_controller.rb b/app/controllers/admin/application_settings_controller.rb
index 9e1dc15de84..6ef7cf0bae6 100644
--- a/app/controllers/admin/application_settings_controller.rb
+++ b/app/controllers/admin/application_settings_controller.rb
@@ -109,6 +109,8 @@ class Admin::ApplicationSettingsController < Admin::ApplicationController
       :sentry_dsn,
       :akismet_enabled,
       :akismet_api_key,
+      :koding_enabled,
+      :koding_url,
       :email_author_in_body,
       :repository_checks_enabled,
       :metrics_packet_size,
diff --git a/app/controllers/koding_controller.rb b/app/controllers/koding_controller.rb
new file mode 100644
index 00000000000..bb89f3090f9
--- /dev/null
+++ b/app/controllers/koding_controller.rb
@@ -0,0 +1,15 @@
+class KodingController < ApplicationController
+  before_action :check_integration!, :authenticate_user!, :reject_blocked!
+  layout 'koding'
+
+  def index
+    path = File.join(Rails.root, 'doc/integration/koding-usage.md')
+    @markdown = File.read(path)
+  end
+
+  private
+
+  def check_integration!
+    render_404 unless current_application_settings.koding_enabled?
+  end
+end