message_broadcast_job.rb

def perform(message, previous_message, current_user)
  # if the message's attribute added_new_users has present values
  # broadcast a notification to those users that they were added to a group conv
  if message.added_new_users.present?
    conversation = message.conversation
    message.added_new_users.each do |user_id|
      ActionCable.server.broadcast(
        "notifications_#{user_id}",
        notification: 'added-to-group-conversation',
        conversation_id: conversation.id,
        message_author: message.user_id,
        link_to_conversation: render_link_to_conversation(conversation, 
                                                          user_id,
                                                          current_user)
      )
    end
  else
    # broadcast message to all conversation's participants
    conversation_id = message.conversation_id
    ActionCable.server.broadcast(
      "group_conversation_#{conversation_id}",
      message: render_message(message, previous_message),
      conversation_id: conversation_id,
      user_id: message.user_id
    )
  end
end