chore: Disable fetching new emails after mailbox error (#4176)

- Disabled email fetch job if credentials for the channel isn't working
- notify customers when the email channel isn't working

fixes: https://github.com/chatwoot/chatwoot/issues/4174

app/mailers/administrator_notifications/channel_notifications_mailer.rb

@@ -15,6 +15,14 @@ class AdministratorNotifications::ChannelNotificationsMailer < ApplicationMailer
     send_mail_with_liquid(to: admin_emails, subject: subject) and return
   end
 
+  def email_disconnect(inbox)
+    return unless smtp_config_set_or_development?
+
+    subject = 'Your email inbox has been disconnected. Please update the credentials for SMTP/IMAP'
+    @action_url = "#{ENV['FRONTEND_URL']}/app/accounts/#{Current.account.id}/settings/inboxes/#{inbox.id}"
+    send_mail_with_liquid(to: admin_emails, subject: subject) and return
+  end
+
   private
 
   def admin_emails