## Layout

[Project] -> [Servers]
[Project] -> [Job Templates]
[Job Template] -> {associated servers} -> [Servers]

{associated servers} contains a `tag` column, if this is = "master" then it should be available to JobTemplate.new().master_server

## Job Template
class JobTemplate < ActiveRecord::Base

  validates_presence_of :description, :project_id

  validates_associated :project

  belongs_to :project

  has_many :associated_servers
  has_one :master_server, :through => :associated_servers, :source => :server, :conditions => ['associated_servers.tag LIKE ?', 'master']

end

## Test (ActiveSupport::TestCase)
  test "having a master server" do
    job_template = Factory( :job_template,
                            :associated_servers => [Factory(:associated_server, :tag => 'master'),
                                                    Factory(:associated_server)])
    debugger
    assert_instance_of Server, job_template.master_server
  end