Fix room sorting for good

Do it the right way with a QSortFilterProxyModel.

harmonyqml/backend/model/items.py

@@ -1,6 +1,6 @@
 from typing import Any, Dict, List, Optional
 
-from PyQt5.QtCore import QDateTime
+from PyQt5.QtCore import QDateTime, QSortFilterProxyModel
 
 from .list_item import ListItem
 from .list_model import ListModel
@@ -20,24 +20,26 @@ class Room(ListItem):
     _required_init_values = {"roomId", "displayName"}
     _constant             = {"roomId"}
 
-    roomId:      str           = ""
-    displayName: str           = ""
-    topic:       Optional[str] = None
-    typingUsers: List[str]     = []
+    roomId:            str                 = ""
+    displayName:       str                 = ""
+    topic:             Optional[str]       = None
+    typingUsers:       List[str]           = []
+    lastEventDateTime: Optional[QDateTime] = None
 
     inviter:   Optional[Dict[str, str]] = None
     leftEvent: Optional[Dict[str, str]] = None
 
 
 class RoomCategory(ListItem):
-    _required_init_values = {"name", "rooms"}
-    _constant             = {"rooms"}
+    _required_init_values = {"name", "rooms", "sortedRooms"}
+    _constant             = {"rooms", "sortedRooms"}
 
     name: str = ""
 
     # Must be provided at init, else it will be the same object
     # for every RoomCategory
-    rooms: ListModel = ListModel()
+    rooms:       ListModel             = ListModel()
+    sortedRooms: QSortFilterProxyModel = QSortFilterProxyModel()
 
 
 class Account(ListItem):