mod_carbons: Carbon incoming message delivery failure reports

Ensures that all your clients know about sent messages that failed.

plugins/mod_carbons.lua

@@ -43,6 +43,10 @@ local function should_copy(stanza, c2s, user_bare)
 		return true, "type";
 	end
 
+	if st_type == "error" and not c2s and not (stanza.attr.from or ""):find("/") then
+		return true, "bounce";
+	end
+
 	return false, "default";
 end