For a model to be designated as an activity provider, we'll need to implement the acts_as_activity_provider plugin that comes with Redmine.

The method's signature for this plugin is as follows:

def acts_as_activity_provider(options = {})

If we're looking to dive directly into the source code for the plugin, it is available as part of our Redmine installation at /path/to/redmine/lib/plugins/acts_as_activity_provider/lib/acts_as_activity_provider.rb.

The acts_as_activity_provider plugin is another class extension plugin and requires us to call the acts_as_activity_provider method within our model's class definition along with some parameters as follows:

class KbArticle < ActiveRecord::Base
  # ...

  acts_as_activity_provider :find_options => {:include => :project},
                            :author_key   => :author_id, 
                            :type         => 'kb_articles',
                            :timestamp    => :updated_at
  # ....