pua_mi: document missing mi_pua_publish parameter "id"

modules/pua_mi/mi_func.c

@@ -41,7 +41,9 @@
  *		<expires>
  *		<event package>
  *		<content_type>     - body type if body of a type different from default
- *                            event content-type or . 
+ *		                     event content-type or .
+ *		<id>               - id for a series of related PUBLISHes to the same
+ *		                     presentity-uri or .
  *		<ETag>             - ETag that publish should match or . if no ETag
  *		<outbound_proxy>   - outbound proxy or .
  *		<extra_headers>    - extra headers to be added to the request or .