WebAuthn WebIDL Questions

Hey guys, I’m not a WebIDL expert but as I’m reading through our WebIDL to
create tests I have a few questions:

   1. I’m assuming that the members of ScopedCredentialOptions
   and AssertionOptions should be nullable types, similar to the example in
   WebIDL 2.2: https://heycam.github.io/webidl/#issue-4d2fc4e6 , right?
   2. According to WebIDL 3.6 interfaces without [NoInterfaceObject] must
   show up on the global `window` object:
   https://heycam.github.io/webidl/#es-interfaces . Do we want to declare
   the WebAuthentication interface with [NoInterfaceObject], since it is
   behaving as a singleton? Note that this is how the geolocation and
   indexeddb interfaces are defined.
   3. Should [SecureContext] only apply to interfaces with operations and /
   or operations themselves (see the note in Secure Contexts Section 2.1:
   https://www.w3.org/TR/secure-contexts/#integration-idl )?
   4. Why are ScopedCredentialInfo, WebAuthnAssertion, WebAuthnAttestation,
   and ScopedCredential interfaces instead of dictionaries?

Thanks,
Adam