Repository Sample
This is a pretty simple repository design and implementation.
I created an interface called Repository, it would store different
sub-repositories operations (e.g. MutantRepository and OrderRepository).
In general, we could just create methods under Resipository interface
(you could decide create another sub-repository to manage like sample or not).
I also created an interface called TransactionHolderRepository, but for what ?
The thing is, for some scenario, we wouldn't have only one service.
Services may use the sample package (e.g. repository) and each service has
their own domain. If we have a serialized operations between services, and make
sure each operation on specifed service is ready, then we would commit these
operation together, or rollback for all of them.
But Repository doesn't let caller own the transaction directly.
So the Repository has TransactionHolderRepository which could create
sub-repository with transaction, make caller could handle the transaction by their own.