WrpClaimPathSegment
A segment of the path pointer of a WrpClaim (ETSI TS 119 475 V1.2.1, B.2.10), which follows the claims path pointer of OpenID4VP (OpenID4VP 1.0, 7): a string selects the key of an object, null all elements of an array, and a non-negative integer the element of an array at that index.