AuthProvider 
A simple authentication provider for Ruby/Rails app. Designed for mobile clients and is compatible with the OAuth 2.0 specification.
Installation
Add this line to your application's Gemfile:
gem 'auth_provider'
And then execute:
$ bundle
Run the installation generator with:
$ rails generate auth_provider:install
This will install the auth_provider initializer into config/initializers/auth_provider.rb, mount AuthProvider::Engine at /oauth in config/routes.rb and copy the database migration file.
At last, don't forget to run:
$ rake db:migrate
Configuration
All the configurations of auth_provider can be found in config/initializers/auth_provider.rb, just check it out!