Right now as part of conversation continuity, we are using the
ConversationReplyMailer which sends a summary of messages including
the incoming messages when an agent replies. Ideally, we want
to send only the reply of that agent and not a summary when
Conversation continuity is enabled. Added the functionality
to send the reply email without summary. Added required unit
tests to cover the changes.
ref: #1048
* Add Conversation factory with dependent factories
* Include FactoryBot methods in rspec config
* Add unit tests for public methods of Conversation model
* Move Current model into a separate file in lib folder
* Disable Metrics/BlockLength rule for db/migrate and spec folders
* Get rid of global $dispatcher variable
* Create Message#unread_since scope
* Refactor callback methods in Conversation model
* Create Conversations::EventDataPresenter
* Add translation keys for activity messages
* Add pry-rails gem
* Refactor Conversation#notify_status_change
* Add mock_redis for test env
