The main idea was to remove internal use of nullable, and to only have one implementation; which is why the synchronous versions call the asynchronous versions.
Rewrote all operation handlers to be async.
This moves the async/sync threshold out into the controller.
Fixed all the uses of cancellation token in the handlers to use the provided cancellation token.
Introduced a new ReusableTransaction that can be passed around, avoiding a ref parameter passing of the transaction instance.
Carl Johnsen