t;auth-dialog&gt; SHOULD be either null or a
    URL where an OAuth 2.0 implicit-grant flow dialog [<a href="#ref-OAUTH">OAUTH</a>] is
    presented.

    If &lt;auth-dialog&gt; is a URL, the user can supply their credentials
    for accessing the account (how, is out of scope), and allow or
    reject a request by the connecting application to obtain a bearer
    token for a certain list of access scopes. Note that an account
    will often belong to just one human user, but may also belong to a
    group 