Add support for Out Of Band authentication
    
    When the `redirect_uri` has a special value for OOB authentication,
    display a page prompting the user to copy and paste the code back to the
    application. Use the code as the page's title as well.
    
    This is useful when it's not practical for the client to run an HTTP
    server and use a `localhost` redirect uri, such as when it's executing
    on a remote machine.
    
    References:
    - https://github.com/googleapis/google-api-python-client/blob/main/docs/oauth-installed.md#urnietfwgoauth20oob
    - https://developers.google.com/identity/protocols/oauth2/native-app#step-2:-send-a-request-to-googles-oauth-2.0-server
    
    Signed-off-by: Aurélien Bompard <aurelien@bompard.org>