authentication.rb

class Authentication
  include DataMapper::Resource

  belongs_to :user
  property :id, Serial
  property :user_id, Integer
  property :provider, String
  property :uid, String, :length => 240
  property :user_name, String, :length => 240
  property :user_email, String, :length => 240
end

project.rb

require 'uuidtools'

class Project
  include DataMapper::Resource
  property :id, UUID, :key => true, :required => true, :default => proc { UUIDTools::UUID.random_create }
  property :name, String

  has 1, :user
end

user.rb

class User
  include DataMapper::Resource

  devise :registerable,   # handles signing up users through a registration process, also edit/destroy account.
         :rememberable,   # "Remember me" from a cookie
         :trackable       # Tracks sign in count, timestamps and IP address
  
  property :id, Serial
  
  # Each user may log in using different methods:
  has n, :authentications
end