如何配置ActionMailer来使用SendGrid的V2 API？

gem 'sendgrid-ruby'
gem 'sendgrid-ruby-rails'

config.action_mailer.delivery_method = :smtp
config.action_mailer.smtp_settings = {
  :address => 'smtp.sendgrid.net',
  :port => 587,
  :user_name => ENV['SENDGRID_USERNAME'],
  :password => ENV['SENDGRID_PASSWORD'],
  :domain => 'yourdomain.com',
  :authentication => :plain,
  :enable_starttls_auto => true
}

class UserMailer < ActionMailer::Base
  default from: 'from@example.com'

  def welcome_email(user)
    @user = user
    mail(to: @user.email, subject: 'Welcome to My Awesome Site')
  end
end

UserMailer.welcome_email(@user).deliver_now