Retry storing LTI data on invalid record

We might receive a `RecordInvalid` error, if one part (such as the external user) is already assigned (not unique). Hence, we just retry.

Fixes CODEOCEAN-TZ

app/controllers/concerns/lti.rb

@@ -226,7 +226,7 @@ module Lti
     @lti_parameters.save!
 
     session[:external_user_id] = current_user.id
-  rescue ActiveRecord::RecordNotUnique
+  rescue ActiveRecord::RecordNotUnique, ActiveRecord::RecordInvalid
     retry
   end