[3xpt] Implement methods:

[MudasirSherwani]

add_item method in the Genre class
should take an instance of the Item class as an input
should add the input item to the collection of items
should add self as a property of the item object (by using the correct setter from the item object)
can_be_archived?() in the MusicAlbum class
should override the method from the parent class
should return true if parent's method returns true AND if on_spotify equals true
otherwise, it should return false