Deleting an item that is still in use (Foreign key violation) should give a nice warning message instead of error dialog

Not sure what's the best way to implement this.

One way is to detect if it's a the foreign-key-violation-exception (often in a causes tree).
But I don't want to have a try-catch around everything, so we probably want to do that generically in the errorDialog handler. In the future, an AuthorizationException will need to be handled in a similar manner.

In any case, these need to be presented as a warning dialog instead of an error dialog (= yellow instead of red) and the message should clearly say something like "The record that you're trying to delete cannot be deleted because it's used by other records."