[1pt] Add all methods visible in the diagram.

[beteland123]

Implement methods:
can_be_archived?() in the Item class
should return true if published_date is older than 10 years
otherwise, it should return false
move_to_archive() in the Item class
should reuse can_be_archived?() method
should change the archived property to true if the result of the can_be_archived?() method is true
should do nothing if the result of the can_be_archived?() method is false