add migration

db/migrate/20190715122930_add_columns_to_oauth_apps.rb

@@ -0,0 +1,14 @@
+require 'carto/db/migration_helper'
+
+include Carto::Db::MigrationHelper
+
+migration(
+  Proc.new do
+    add_column :oauth_apps, :description, String, null: true
+    add_column :oauth_apps, :website_url, String, null: true
+  end,
+  Proc.new do
+    drop_column :oauth_apps, :description
+    drop_column :oauth_apps, :website_url
+  end
+)