groupchat message with both subject and body should not be treated as subject change
The subject is changed by sending a message of type "groupchat" to the <room@service>, where the
<message/>MUST contain a
<subject/>element that specifies the new subject but MUST NOT contain a
<body/>element (or a
<thread/>element). In accordance with the core definition of XMPP, other child elements are allowed (although the entity that receives them might ignore them).
Note: A message with a
<thread/>is a legitimate message, but it SHALL NOT be interpreted as a subject change.
This is a topic change:
<message type="groupchat"> <subject>Fire Burn and Cauldron Bubble!</subject> </message>
This is not a topic change:
<message type="groupchat"> <subject>Did you know</subject> <body>Normal groupchat messages can have a subject line</body> </message>
Neither is this:
<message type="groupchat"> <subject>Threads, how do they work?</subject> <thread>eb07d7b1-7b6c-4067-a540-cbd0c29285cd</thread> </message>