Description of feature:
When eg adding member affiliation to a jid we get an affiliation update:
```
<message from="mucjid">
<x xmlns="http://jabber.org/protocol/muc#user">
<item affiliation="member" jid="newuser"/>
</x>
</message>
```
It would be very useful to also receive the occupant-id as part of this:
```
<message from="mucjid">
<x xmlns="http://jabber.org/protocol/muc#user">
<item affiliation="member" jid="newuser">
<occupant-id xmlns="urn:xmpp:occupant-id:0" id="blahblahoccupantid"/>
</item>
</x>
</message>
```
Motivation:
Right now when I invite someone to an invite-old room, I don't know what their occupant id will be, and so I cannot store them in any client data structured which are keyed by occupant id until later when they join.
Description of feature: When eg adding member affiliation to a jid we get an affiliation update: ``` <message from="mucjid"> <x xmlns="http://jabber.org/protocol/muc#user"> <item affiliation="member" jid="newuser"/> </x> </message> ``` It would be very useful to also receive the occupant-id as part of this: ``` <message from="mucjid"> <x xmlns="http://jabber.org/protocol/muc#user"> <item affiliation="member" jid="newuser"> <occupant-id xmlns="urn:xmpp:occupant-id:0" id="blahblahoccupantid"/> </item> </x> </message> ``` Motivation: Right now when I invite someone to an invite-old room, I don't know what their occupant id will be, and so I cannot store them in any client data structured which are keyed by occupant id until later when they join.