w3c/webauthn@a133711 (w3c/webauthn#1392)

Web Authentication just dropped their uses of enums because it's not forward compatible; older implementation throws when passing a newly added enum value. They now use DOMString and have proses to ignore unknown enum values:

Client platforms MUST ignore unknown values, treating an unknown value as if the member does not exist.

Should this be supported in IDL level? Is there any other specification that does the same thing?