Grapify the settings API

doc/api/settings.md

@@ -79,6 +79,7 @@ PUT /application/settings
 | `enabled_git_access_protocol` | string | no | Enabled protocols for Git access. Allowed values are: `ssh`, `http`, and `nil` to allow both protocols. |
 | `koding_enabled` | boolean | no | Enable Koding integration. Default is `false`. |
 | `koding_url` | string | yes (if `koding_enabled` is `true`) |  The Koding instance URL for integration. |
+| `disabled_oauth_sign_in_sources` | Array of strings | no | Disabled OAuth sign-in sources |
 
 ```bash
 curl --request PUT --header "PRIVATE-TOKEN: 9koXpg98eAheJpvBs5tK" https://gitlab.example.com/api/v3/application/settings?signup_enabled=false&default_project_visibility=1

spec/requests/api/settings_spec.rb

@@ -44,8 +44,7 @@ describe API::Settings, 'Settings', api: true  do
         put api("/application/settings", admin), koding_enabled: true
 
         expect(response).to have_http_status(400)
-        expect(json_response['message']).to have_key('koding_url')
-        expect(json_response['message']['koding_url']).to include "can't be blank"
+        expect(json_response['error']).to eq('koding_url is missing')
       end
     end
   end