I've proposed some changes in https://github.com/rvansa/hibernate-orm/tree/HHH-11356

I think we could replace SharedSessionContractImplementor, which was used just to find out the tx start timestamp, and in hibernate-infinispan to register a new synchronizations with this one. As there's no API to list currently registered synchronizations on a transaction, I used to register many syncs. CacheSynchronization provides single place to deal with this.