Re: [webauthn] residentKey: "preferred-if-unlimited"? (#1822)

Looking at L2 we don't need a spec change.
preferred
This value indicates the [Relying Party](https://www.w3.org/TR/webauthn-2/#relying-party) strongly prefers creating a [client-side discoverable credential](https://www.w3.org/TR/webauthn-2/#client-side-discoverable-credential), but will accept a [server-side credential](https://www.w3.org/TR/webauthn-2/#server-side-credential). For example, user agents SHOULD guide the user through setting up [user verification](https://www.w3.org/TR/webauthn-2/#user-verification) if needed to create a [client-side discoverable credential](https://www.w3.org/TR/webauthn-2/#client-side-discoverable-credential) in this case. This takes precedence over the setting of [userVerification](https://www.w3.org/TR/webauthn-2/#dom-authenticatorselectioncriteria-userverification).

The platform can already use its judgement on how to treat a strong RP preference.
Before CTAP2.1 the platform did not know how many resident slots remained.   
Perhaps this would be more appropriate for the CTAP2.2 platform guidance to have a non normative note in making the credential that if webauthn is set to preferred then rk=true should only be sent if remainingDiscoverableCredentials has a value of 25 or greater.

I don't think we need a change in WebAuthn.

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Received on Thursday, 10 November 2022 12:43:27 UTC