@Nullable
    public String getSharedDisplayName() {
        return getProperties().get(SHARED_ROSTER_DISPLAY_NAME_PROPERTY_KEY);
    }
When contact list group sharing has been enabled, the users in his group will be added to the contact list of
every entity that the group is shared with. On their contact lists, the users from this group will be added
to a group by a name that is equal to the return value of this method.

This method may return a null value when contact list sharing has not yet been configured, or an empty string
when it has explicitly been configured to be disabled ("share with nobody").

@return A name to be used for a contact list group when sharing is enabled.
xmppserver/src/main/java/org/jivesoftware/openfire/group/Group.java