feat: Tag agents in a private note (#1688)

Co-authored-by: Sojan <sojan@pepalo.com>

app/mailers/agent_notifications/conversation_notifications_mailer.rb

@@ -19,6 +19,16 @@ class AgentNotifications::ConversationNotificationsMailer < ApplicationMailer
     send_mail_with_liquid(to: @agent.email, subject: subject) and return
   end
 
+  def conversation_mention(message, agent)
+    return unless smtp_config_set_or_development?
+
+    @agent = agent
+    @conversation = message.conversation
+    subject = "#{@agent.available_name}, You have been mentioned in conversation [ID - #{@conversation.display_id}]"
+    @action_url = app_account_conversation_url(account_id: @conversation.account_id, id: @conversation.display_id)
+    send_mail_with_liquid(to: @agent.email, subject: subject) and return
+  end
+
   def assigned_conversation_new_message(conversation, agent)
     return unless smtp_config_set_or_development?
     # Don't spam with email notifications if agent is online