...and then extending the class Mage_SalesRule_Model_Resource_Rule_Collection and overriding the method named addWebsiteGroupDateFilter to pass comma separated group id in the join query.
Can you explain this a little more thoroughly? I did the first part and it works in the admin panel but if the customer tries to login it throws an error. I’m thinking its because I haven’t done the second part but cant figure out where those classes are to extend.
Any insight would be greatly appreciated!
EDIT: I found the class in app/code/core/Mage/SalesRule/Model/Resource/Rule/Collection.php but am unsure what changes need to be made to pass the group id as comma separated.