locateUrl

Resolves the URL a metadata document is hosted at for a given vct (used both as document identity and for walking extends). Required because a vct is not necessarily a URL (e.g. urn:eudi:pid:1); the owning at.asitplus.wallet.lib.data.CredentialMetadataRegistry keeps the actual vct -> URL mapping and supplies this lookup. A vct for which this returns null cannot be fetched, and retrieve returns null for it.