Show QR code for OAuth device authentication

When the OAuth device response includes the verification_uri_complete parameter, it would be neat to show a QR code to help open this URL on another device.

https://datatracker.ietf.org/doc/html/rfc8628#section-3.3.1

When "verification_uri_complete" is included in the authorization response, clients MAY present this URI in a non-textual manner using any method that results in the browser being opened with the URI, such as with QR (Quick Response) codes or NFC (Near Field Communication), to save the user from typing the URI.

For usability reasons, it is RECOMMENDED for clients to still display the textual verification URI ("verification_uri") for users who are not able to use such a shortcut. Clients MUST still display the "user_code", as the authorization server will require the user to confirm it to disambiguate devices or as remote phishing mitigation.

            +-------------------------------------------------+
            |                                                 |
            |  Scan the QR code or, using     +------------+  |
            |  a browser on another device,   |[_]..  . [_]|  |
            |  visit:                         | .  ..   . .|  |
            |  https://example.com/device     | . .  . ....|  |
            |                                 |.   . . .   |  |
            |  And enter the code:            |[_]. ... .  |  |
            |  WDJB-MJHT                      +------------+  |
            |                                                 |
            +-------------------------------------------------+

Start by locating the OAuth device authentication flow that handles verification_uri_complete, then review RFC 8628 section 3.3.1 and the existing user-facing output. Done means displaying a QR code when the parameter is present while retaining the verification URI and user code for users who cannot scan it.