Use exceptions to handle database conflicts and stuff

[Atulin]

Currently, a lot is done by fetching the item from the database or otherwise querying it before inserting a new record to perform various checks. Database exceptions could be used instead, but they're complete unadulterated garbage, you have to do shit like

catch (SomeDatabaseException e) where e.InnerException.Code == 261

or whatever.

Thankfully, this package exists so let's use it.