Update mod_muc_room to support XEP-0425 0.3.0 (VERY EARLY DRAFT)

[badlop]

ejabberd allows a MUC occupant to retract a message he has sent, using XEP-0424: Message Retraction.

It is also possible for a room moderator to retract a message sent by another occupant, using XEP-0425: Moderated Message Retraction.

Right now ejabberd implements XEP-0425 0.2.1, as documented in

ejabberd/src/mod_mam.erl

Line 31 in 426e33d

-protocol({xep, 425, '0.2.1', '23.04', "", ""}).

There's a new version of XEP-0425, 0.3.0: xsf/xeps@ef79d2c

Here is a very dirty early and unfinished patch to support that XEP version:

diff --git a/src/mod_muc_room.erl b/src/mod_muc_room.erl
index 72ec867be..88528ed76 100644
--- a/src/mod_muc_room.erl
+++ b/src/mod_muc_room.erl
@@ -503,6 +503,10 @@ normal_state({route, <<"">>,
 			       process_iq_adhoc(From, IQ, StateData);
 			   #register{} ->
                                mod_muc:process_iq_register(IQ);
+			   #message_moderate{} ->
+			       Id = (SubEl#message_moderate.retract)#message_retract.id,
+			       ApplyTo = #fasten_apply_to{id = Id},
+			       process_iq_moderate(From, IQ, ApplyTo, SubEl, StateData);
 			   #fasten_apply_to{} = ApplyTo ->
 			       case xmpp:get_subtag(ApplyTo, #message_moderate{}) of
 				   #message_moderate{} = Moderate ->

After applying this patch, a room moderator can send to the room:

<iq type='set' to='room1@conference.localhost' id='retract-request-1'>
  <moderate xmlns='urn:xmpp:message-moderate:0'>
    <retract id="1712326927080870" xmlns='urn:xmpp:message-retract:1'/>
    <reason>This message contains inappropriate content for this forum</reason>
  </moderate>
</iq>

---

Interestingly, there seems to be a bug in XEP-0425 itself:

• XEP-0424 schema says:

  <xs:element name='retract'>
    <xs:attribute name='id' type='xs:string' use='required'/>
  </xs:element>

• but later, in XEP-0425 example, when a retract element is used, it doesn't include id:

<retract xmlns='urn:xmpp:message-retract:1'/>

• Instead, the id is provided in the new moderate element:

<moderate id="stanza-id-1" xmlns='urn:xmpp:message-moderate:1'>