It's not implied. If you want to use `item.user`, you have to define. If you don't need to use `item.user`, you don't need to define it.
jdeen rule #1: don't go from 3 to 5. Go from 3 to 3.1, to 3.2, then 4.0, then 4.1, then 4.2, then 5, then 5.1, then 5.2.
jdeen it is not possible to do a correct assessment without knowing the version you were and which one you're updating to. Generally, the changelogs and migration docs will not include changes as long as from 3 to 5.