add login

app/models/user.rb

@@ -4,3 +4,10 @@ class User < ActiveRecord::Base
   devise :database_authenticatable, :registerable,
          :recoverable, :rememberable, :trackable, :validatable
 end
+
+class User::ParameterSanitizer < Devise::ParameterSanitizer
+  def initialize(*)
+    super
+    permit(:sign_up, keys: [:username, :email])
+  end
+end