title: Rails / Papertrail: Changeset with association changes
body: <p>I am stuck. I've been trying to figure out how to include the association changes (<code>has_many</code>, <code>has_many through</code>) on a model that has papertrail. I would like to call <code>MyModel.versions.first.changeset</code> and have any changes that took place on associated objects be included in the <code>.changeset</code> hash that is returned from that version of the object. </p>
  
  <p>I've added the migrations for version associations:</p>
  
  <pre><code>class CreateVersionAssociations &lt; ActiveRecord::Migration
    def self.up
      create_table :version_associations do |t|
        t.integer  :version_id
        t.string   :foreign_key_name, :null =&gt; false
        t.integer  :foreign_key_id
      end
      add_index :version_associations, [:version_id]
      add_index :version_associations, [:foreign_key_name, :foreign_key_id], :name =&gt; 'index_version_associations_on_foreign_key'
    end
  
    def self.down
      remove_index :version_associations, [:version_id]
      remove_index :version_associations, :name =&gt; 'index_version_associations_on_foreign_key'
      drop_table :version_associations
    end
  end
  
  
  class AddTransactionIdColumnToVersions &lt; ActiveRecord::Migration
    def self.up
      add_column :versions, :transaction_id, :integer
      add_index :versions, [:transaction_id]
    end
  
    def self.down
      remove_index :versions, [:transaction_id]
      remove_column :versions, :transaction_id
    end
  end
  </code></pre>
  
  <p>I have added Papertrail to the associated objects, but as far as I can tell, there is no documentation discussing retrieving changes that took place on the associated objects. Can anyone assist on if this is possible using Papertrail?</p>
  
  <p>I am trying to implement an audit trail of changes on a model and its associated objects that can be accessed in one changeset.</p>