In the docs we have https://developers.hubspot.com/docs/guides/api/crm/associations/associations-v3 showing the active endpoint that the assocationsApi would have ended up at but from v11 we have:
Removed crm()->objects()->associationsApi().
I can see there is similar on v4 existing but without using v4 it looks as though the only functionality around associations on v3 would be via batchApi?