Use idiomatic references to iin and last digits

Author: ugexe

CHANGELOG.md

@@ -22,16 +22,15 @@ CHANGELOG
   `response.ipAddress.traits.mobileCountryCode` and
   `response.ipAddress.traits.mobileNetworkCode`. We expect this data to be
   available by late January, 2022.
-* The `/credit_card/last4digits` input has been deprecated in favor of
-  `/credit_card/lastDigits` and will be removed in a future release.
-  `lastDigits`/`last4digits` also now supports two digit values in
-  addition to the previous four digit values.
-* Eight digit `/credit_card/issuerIdNumber` inputs are now supported in
-  addition to the previously accepted six digit `issuerIdNumber`. In most
-  cases, you should send the last four digits for `lastDigits`. If you send
-  an `issuerIdNumber` that contains an eight digit IIN, and if the credit
-  card brand is not one of the following, you should send the last two digits
-  for `lastDigits`:
+* `creditCard.last4digits` has been deprecated in favor of `creditCard.lastDigits`
+   and will be removed in a future release. `lastDigits`/`last4digits` also now
+   supports two digit values in addition to the previous four digit values.
+* Eight digit `creditCard.issuerIdNumber` inputs are now supported in addition to
+  the previously accepted six digit `issuerIdNumber`. In most cases, you should
+  send the last four digits for `creditCard.lastDigits`. If you send a
+  `issuerIdNumber` that contains an eight digit IIN, and if the credit card brand
+  is not one of the following, you should send the last two digits for
+  `lastDigits`:
   * `Discover`
   * `JCB`
   * `Mastercard`