Changes to List all add-ons

added the new SYP enum value to the add_ons/items/amount_currency response property for the response status 200

added the new TND enum value to the add_ons/items/amount_currency response property for the response status 200

added the optional property add_ons/items/taxes/items/applied_to_billing_entities_codes to the response with the 200 status

the response property add_ons/items/taxes became required for the status 200

the response property add_ons/items/taxes/items/description became required for the status 200