adjust invite email

app/mailers/user_mailer.rb

@@ -9,6 +9,6 @@ class UserMailer < ApplicationMailer
     assign_message_metadata('user_invitation', @user)
 
     mail(to: @user.friendly_name,
-         subject: 'You are invited to DocuSeal')
+         subject: "You are invited to #{Docuseal.product_name}")
   end
 end