Is AuthenticationExtensionsAuthenticatorInputs unused?

[emlun]

§5.7.3 lists the definition:

typedef record<DOMString, DOMString> AuthenticationExtensionsAuthenticatorInputs;

...which seems to not be referenced anywhere else in the spec, and extensions certainly use output types other than DOMString. Is this type unused?

While working on #1425 I started thinking about adding a simlar CDDL extension point. Should we perhaps transmute it into CDDL (as WebIDL doesn't seem entirely appropriate for the authenticator layer) and update it to match the extensions?