Changes to Create an add-on

added the non-success response with the status 404

the add_on/amount_cents request property's min was set to 1.00

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

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

added the new SYP enum value to the request property add_on/amount_currency

added the new TND enum value to the request property add_on/amount_currency

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

the response property add_on/taxes became required for the status 200

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