Try to improve transactional behavior

[OndroMih]

Currently, transactions are bound to a thread.

Is it possible to begin a tx in one thread and commit in another one?
Is it possible to move the transaction context using the contextService around?
Is it possible to bind execution of the callbacks to a single thread if not possible to move the transaction around? (e.g. by a custom managed executor?)

[OndroMih]

Experimented with moving Tx context via contextService and use UserTransaction to begin and commit in different threads, in [try_transaction_propagation}(https://github.com/OndrejM-demonstrations/Reactive-CargoTracker/tree/try_transaction_propagation) branch.

It didn't work, tx was not active in another thread, even within the contextualProxy.