luhn: Apply new "input" policy (#1054)
luhn: Apply new "input" policy (#1054)

* luhn: Apply new "input" policy

Per #996

* luhn: change "ccNumber" to "value"

jmluy/x-common,rpottsoh/x-common,petertseng/x-common,ErikSchierboom/x-common,ErikSchierboom/x-common,petertseng/x-common,exercism/x-common,jmluy/x-common,exercism/x-common,rpottsoh/x-common,jmluy/x-common