xep0060: pubsub-items-retract needs to allow list of ids to retract

[sstrigler]

No description provided.

[badlop]

Right, this is explained in https://xmpp.org/extensions/xep-0060.html#impl-batch

A publisher MAY include multiple elements in a publish request and MAY include multiple elements in a retract request. This results in "batch processing" of publications or retractions.

and detailed in https://xmpp.org/extensions/xep-0060.html#schemas-event

  <xs:element name='items'>
    <xs:complexType>
      <xs:choice>
        <xs:element ref='item' minOccurs='0' maxOccurs='unbounded'/>
        <xs:element ref='retract' minOccurs='0' maxOccurs='unbounded'/>
      </xs:choice>
      <xs:attribute name='node' type='xs:string' use='required'/>
    </xs:complexType>
  </xs:element>