macOS Swift: How to properly add application as Login Item

Question

I have spent about one day (maybe a little more) on trying to add my application to Login Item in the order it starts up at macOS launch (user login).

1. The fir

Answer 1

The above solution of Login Item programming problem works correctly both using modern approach with ServiceManagement.framework, and old (deprecated) approach with inserting Login Item into System Preferences > Users & Groups > Login Items. See my UPDATE 1 and UPDATE 2 remarks.