This method attempts to invite a contact to the conversation. If a user is having a conversation with
another contact, both the user and the other contact can invite additional participants to the conversation.
When the invite operation completes, the InviteAddressCompleted event is raised. This
event should be handled to determine whether the contact was successfully invited to the conversation.
An invitation can fail if the other contact went offline while the invite was in transit or if the invited
contact doesn't support multiparty chat.
Once an invited contact joins a conversation, the CollectionChanged event
is raised on the Roster property. This event should be handled to detect changes in the