Support for authenticatorDisplayName (Client extension output)

[maui1911]

authenticatorDisplayName, of type [USVString](https://webidl.spec.whatwg.org/#idl-USVString)

This OPTIONAL property is a human-palatable description of the credential’s managing authenticator, chosen by the user.

The client MUST allow the user to choose this value. That choice MAY be presented during the registration or authentication ceremony or MAY be made available outside the ceremony, for example in client settings. The client MAY reuse the same value for multiple credentials with the same managing authenticator across multiple Relying Parties.

The client MAY query the authenticator, by some unspecified mechanism, for this value. The authenticator MAY allow the user to configure the response to such a query. The authenticator vendor MAY provide a default response to such a query. The client MAY consider a user-configured response chosen by the user, and SHOULD allow the user to modify a vendor-provided default response.

If the Relying Party includes an authenticatorDisplayName item in its credential records, the Relying Party MAY offer this authenticatorDisplayName extension output, if present, as a default value for the authenticatorDisplayName of the new credential record it stores after a registration ceremony.

If the authenticatorDisplayName extension output from an authentication ceremony is different from the authenticatorDisplayName of the credential record, the Relying Party MAY offer the user to update the authenticatorDisplayName of the credential record.

https://w3c.github.io/webauthn/#dom-credentialpropertiesoutput-authenticatordisplayname