Add external authorization timeout to settings

This will allow us to configure the timeout when calling the external
authorization service.

db/schema.rb

@@ -11,7 +11,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema.define(version: 20180309160427) do
+ActiveRecord::Schema.define(version: 20180314100728) do
 
   # These are extensions that must be enabled in order to support this database
   enable_extension "plpgsql"
@@ -184,6 +184,7 @@ ActiveRecord::Schema.define(version: 20180309160427) do
     t.string "external_authorization_service_url"
     t.string "external_authorization_service_default_label"
     t.boolean "pages_domain_verification_enabled", default: true, null: false
+    t.float "external_authorization_service_timeout", default: 0.5, null: false
   end
 
   create_table "approvals", force: :cascade do |t|

ee/db/migrate/20180314100728_add_external_authorization_service_timeout_to_application_settings.rb

+class AddExternalAuthorizationServiceTimeoutToApplicationSettings < ActiveRecord::Migration
+  include Gitlab::Database::MigrationHelpers
+
+  DOWNTIME = false
+
+  def up
+    # We can use the regular `add_column` with a default since `application_settings`
+    # is a small table.
+    add_column :application_settings,
+               :external_authorization_service_timeout,
+               :float,
+               default: 0.5
+  end
+
+  def down
+    remove_column :application_settings, :external_authorization_service_timeout
+  end
+end