 types of Actors:
        <code><a href="https://www.w3.org/TR/activitystreams-vocabulary/#dfn-application">Application</a>
        </code> |
        <code><a href="https://www.w3.org/TR/activitystreams-vocabulary/#dfn-group">Group</a></code> |
        <code><a href="https://www.w3.org/TR/activitystreams-vocabulary/#dfn-organization">Organization</a></code> |
        <code><a href="https://www.w3.org/TR/activitystreams-vocabulary/#dfn-person">Person</a></code> |
        <code><a href="https://www.w3.org/TR/