add devise gem for authentication

1. sign up - hashed password, confirmation(email), forgot password, remember user

2. login

3. log out

 

gemfile에 추가

gem 'devise'

devise 설치하고 User model 생성, migrate

bundle install --without production
rails generate devise:install
rails generate devise User
rails db:migrate

controller에 before_action 추가

before_action :authenticate_user!

참고: github.com/heartcombo/devise#starting-with-rails

heartcombo/devise