Assume CC numbers are strings
Assume CC numbers are strings

We honestly should be doing this anyway; now, enforce it, and take
advantage of it to cut down on string conversions.

Follow-up to conversation in #2983

3926 tests, 68184 assertions, 0 failures, 0 errors, 0 pendings, 2 omissions, 0 notifications
100% passed

whitby3001/active_merchant