It will be more convinient, in my opinion, to distinguish projects as active and inactive.

It will be more convinient, in my opinion, to distinguish projects as active and inactive.
As for me, it is convinient to use projects to account the cost of short-term events, like business-trips, e.t.c.
Due to the id-reference relation "transaction-project" one shouldn't delete project after the end of event.
Also, it is inconvinient to dig in long projects list while new transation is creating.
Due do this, I suggest additional attribute of Project entity - boolean "isActive".
Request Code Reviev.