Add devise

app/models/user.rb

@@ -0,0 +1,13 @@
+class User < ApplicationRecord
+  # Include default devise modules. Others available are:
+  # :confirmable, :lockable, :timeoutable, :trackable and :omniauthable
+  devise :database_authenticatable, :registerable, :rememberable
+
+  def email_required?
+    false
+  end
+
+  def email_changed?
+    false
+  end
+end