add the is_default field to the PaymentMethod model in payment_method.py
add a new route to handle the setting of a default payment method in routes.py
add tests for for is_default field in TestPaymentMethodModel in test_models.py
include the is_default field in factory functions
add a test case in TestPaymentsService class in test_routes.py
add the is_default field to the PaymentMethod model in payment_method.py add a new route to handle the setting of a default payment method in routes.py add tests for for is_default field in TestPaymentMethodModel in test_models.py include the is_default field in factory functions add a test case in TestPaymentsService class in test_routes.py