```ruby
require 'sg_mailer/configuration_error'
require 'sg_mailer/response_error'
require 'sg_mailer/mail_builder'
require 'sg_mailer/client'
require 'sg_mailer/test_client'
require 'sg_mailer/message_delivery'
require 'sg_mailer/base'

module SGMailer extend self
  attr_accessor :client

  def configure(test_client: false, **options)
    self.client =
      if test_client
        TestClient.new
      else
        Client.new(**options)
      end
  end

  def send(mail)
    raise ConfigurationError if client.nil?

    client.send(mail)
  end
end
```

Add an option to configure the delivery processor
user
```ruby
require 'sg_mailer/configuration_error'
require 'sg_mailer/response_error'
require 'sg_mailer/mail_builder'
require 'sg_mailer/client'
require 'sg_mailer/test_client'
require 'sg_mailer/message_delivery'
require 'sg_mailer/base'

module SGMailer extend self
  attr_accessor :client
  attr_accessor :delivery_processor

  def configure(delivery_processor: MessageDelivery,
                test_client: false, **client_options)
    self.client = test_client ? TestClient.new : Client.new(**options)
    self.delivery_processor = delivery_processor || MessageDelivery
  end

  def send(mail)
    raise ConfigurationError if client.nil?

    client.send(mail)
  end
end
```
assistant