* initial proposal of payment card validation #788
* some cleanup for PaymentCardNumber #788
* fix linting issues
* tests and more robust errors #788
* fixed linting
* fixing mypy errors
* let's try this to make mypy work
* make consistent with cpython tests
* avoid using __new__
* use __init__ instead of properties
* clean up PaymentCardNumber.__init__
* use ClassVar where applicable
* add to changes/
* turns out this is never used
* get brand for other
* clean up a bit
* make PaymentCardNumber private
* use if/else to make faster in cython
* card_number => card number in errors
* make it clearer in the tests which exception is being raised
* parameterize tests for PaymentCardNumber
* lint
* clean up merge mistake from earlier
* fix mypy test error
* take out commented line
* update comment since code is moved
* docs for PaymentCardNumber
* clean up docs for PaymentCardNumber
* var name that makes more sense
Matin Tamizi
0c5793770b