add admin user by devise

app/models/admin_user.rb

@@ -0,0 +1,7 @@
+# frozen_string_literal: true
+class AdminUser < ApplicationRecord
+  # Include default devise modules. Others available are:
+  # :confirmable, :lockable, :timeoutable, :trackable and :omniauthable
+  devise :database_authenticatable, :recoverable,
+    :rememberable, :validatable
+end