bookstore/app/controllers/sessions_controller.rb

class SessionsController < ApplicationController
  def new
  end

  def create
    @user = User.find_by(username: params[:username])
    if @user && @user.authenticate(params[:password])
      sessions[:user_id] = @user.id
    end
    redirect_to '/welcome'
  end

  def welcome
  end
end