Merge branch '24059-round-robin-repository-storage' into 'master'

Resolve "Introduce round-robin project creation to spread load over multiple shards"

## What does this MR do?

Allow multiple shards to be enabled in the admin settings page, balancing project creation across all enabled shards.

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

* `f.select ..., multiple: true` isn't the most beautiful UI in the world, but switching to `collection_check_boxes` (or a facsimile thereof) isn't trivial
* Should `pick_repository_storage` be a method of `ApplicationSetting`, or `Project`? It's going to accrete logic over time so perhaps it should be its own class already?
* This is written to avoid the need for a database migration, so it is`serialize :repository_storage` without `, Array`. This is tested, but alternatives include:
  * Add a database migration
  * Write a custom Coder that will accept a String or Array in `load` and always `dump an Array.

## Why was this MR needed?

## Screenshots (if relevant)

![Screen_Shot_2016-11-03_at_14.42.41](/uploads/7de15d6c1b3fa60bb7a34d6a7d9f00ce/Screen_Shot_2016-11-03_at_14.42.41.png)

## Does this MR meet the acceptance criteria?

- [X] [CHANGELOG](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CHANGELOG.md) 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 [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 #24059

See merge request !7273

2 files changed, 3 insertions, 2 deletions

diff --git a/lib/api/entities.rb b/lib/api/entities.rb
index d52496451a2..1f378ba1635 100644
--- a/lib/api/entities.rb
+++ b/lib/api/entities.rb
@@ -509,6 +509,7 @@ module API
       expose :after_sign_out_path
       expose :container_registry_token_expire_delay
       expose :repository_storage
+      expose :repository_storages
       expose :koding_enabled
       expose :koding_url
     end
diff --git a/lib/api/settings.rb b/lib/api/settings.rb
index c885fcd7ea3..c4cb1c7924a 100644
--- a/lib/api/settings.rb
+++ b/lib/api/settings.rb
@@ -17,12 +17,12 @@ module API
       present current_settings, with: Entities::ApplicationSetting
     end
 
-    # Modify applicaiton settings
+    # Modify application settings
     #
     # Example Request:
     #   PUT /application/settings
     put "application/settings" do
-      attributes = current_settings.attributes.keys - ["id"]
+      attributes = ["repository_storage"] + current_settings.attributes.keys - ["id"]
       attrs = attributes_for_keys(attributes)
 
       if current_settings.update_attributes(attrs)