[2 xpt] create item class

[Bhushan Deshmukh]

• All Item class properties visible in the diagram should be defined and set up in the constructor method. Exception: properties for the 1-to-many relationships should NOT be set in the constructor method. Instead, they should have a custom setter method created.
• Add all methods visible in the diagram.
• 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