* stub out COD payment method for checkout block
* consistently use sentence case for (default) payment tab labels
* expose COD `enable_for_virtual` option to client
* correct docblock return value comment Stripe::get_inline_cc_form()
* allow merchant to disable COD payment for virtual/downloadable orders
* tweak canMakePayment dev docs - add cart-dependent example use case
* only allow (show) COD if initially-selected shipping method(s) allow
* tweak `canMakePayment` payment extension API docs
* use $VID:$ substitution for `@since` version in new payment methods
* use FILTER_VALIDATE_BOOLEAN for payment method boolean options
* use more semantic `some` when hunting for COD-unsupported shipping
* clarify `canMakePayment` API docs
* re-select payment method if selected method disappears (e.g. COD) +
+ factor out early return into separate if at top for clarity
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