Ruby on Rails: How to bypass Model validation

gistfile1.rb

#Ruby on Rails: How to bypass Model validation
#User Model
class User < ActiveRecord::Base
  validates_presence_of :first_name, :last_name
end

#BusinessAccount Model
class BusinessAccount < ActiveRecord::Base
  validates_uniqueness_of :username 
  validates_presence_of :username, :category, :name
end

#Signup Controller
class SignupController < ApplicationController
  
  def new
    @user =  User.new
    @business_account = BusinessAccount.new
  end
  
  def create
    @user = User.new(params[:user])
    @business_account = BusinessAccount.new(params[:business_account])
    
    if @user.save
      @business_account.user_id = @user.id
      @business_account.save_with_validation(false) # This is the line all the magic happens
      render :action => 'checkout'
    else
      render :action => 'new'
    end
  end
end