Devise

Devise is a flexible authentication solution for Rails that is based on Warden, a general Rack authentication framework. It is a complete MVC solution based on Rails engines that lets you have several models signed in at the same time. It consists of 10 modules:
1. Authenticatable Module, responsible for password hashing and validating user authenticity when signing in
2. Omniauthable adds OmniAuth support
3. Confirmable is responsible for verifying if an account is already confirmed during sign in
4. Recoverable oversees the resetting of the user password and sends reset instructions
5. Registerable handles all aspects related to registering a new resource
6. Rememberable takes care of generating and clearing token for remembering the user from a saved cookie
7. Trackable tracks info about user sign in
8. Timeoutable expires inactive sessions
9. Validatable provides email and password validations, and lastly
10. Lockable, which locks an account after some failed sign-ins