OmniAuth
OmniAuth is a flexible authentication system utilizing Rack middleware
... as RubyGems, and you can see a community-maintained list on the wiki for this project. One strategy, called Developer, is included with OmniAuth and provides a completely insecure, non-production-usable strategy that directly prompts a user for authentication information and then passes it straight through. You can use it as a placeholder when you start development and easily swap in other strategies later.