omniauth strategy

db/migrate/20161017160526_create_users.rb

@@ -0,0 +1,15 @@
+class CreateUsers < ActiveRecord::Migration[5.0]
+  def change
+    create_table :users do |t|
+      t.string :provider, null: false
+      t.string :uid, null: false
+      t.string :name
+
+      t.timestamps
+    end
+
+    add_index :users, :provider
+    add_index :users, :uid
+    add_index :users, [:provider, :uid], unique: true
+  end
+end