[2pt] Implement methods for MusicAlbum

[ciraganenicole]

Implement methods:

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 the parent's method returns true AND if on_spotify equals true
• otherwise, it should return false