Chore: Refactor round robin logic (#1015)

Co-authored-by: Pranav Raj S <pranav@thoughtwoot.com>

app/models/message.rb

@@ -153,7 +153,6 @@ class Message < ApplicationRecord
   end
 
   def notify_via_mail
-    conversation_mail_key = Redis::Alfred::CONVERSATION_MAILER_KEY % conversation.id
     if Redis::Alfred.get(conversation_mail_key).nil? && conversation.contact.email? && outgoing?
       # set a redis key for the conversation so that we don't need to send email for every
       # new message that comes in and we dont enque the delayed sidekiq job for every message
@@ -165,6 +164,10 @@ class Message < ApplicationRecord
     end
   end
 
+  def conversation_mail_key
+    format(::Redis::Alfred::CONVERSATION_MAILER_KEY, conversation_id: conversation.id)
+  end
+
   def validate_attachments_limit(_attachment)
     errors.add(attachments: 'exceeded maximum allowed') if attachments.size >= NUMBER_OF_PERMITTED_ATTACHMENTS
   end