Define ToggleEntity entity attributes as class variables (#51231)

* Define ToggleEntity entity attributes as class variables

* Fix upcloud overriding state property

* Implement available state for upcloud, to compensate removed state

homeassistant/components/upcloud/__init__.py

@@ -273,18 +273,20 @@ class UpCloudServerEntity(CoordinatorEntity):
         """Return the icon of this server."""
         return "mdi:server" if self.is_on else "mdi:server-off"
 
-    @property
-    def state(self) -> str | None:
-        """Return state of the server."""
-        try:
-            return STATE_MAP.get(self._server.state, self._server.state)
-        except AttributeError:
-            return None
-
     @property
     def is_on(self) -> bool:
         """Return true if the server is on."""
-        return self.state == STATE_ON
+        try:
+            return STATE_MAP.get(self._server.state, self._server.state) == STATE_ON
+        except AttributeError:
+            return False
+
+    @property
+    def available(self) -> bool:
+        """Return True if entity is available."""
+        return super().available and STATE_MAP.get(
+            self._server.state, self._server.state
+        ) in [STATE_ON, STATE_OFF]
 
     @property
     def extra_state_attributes(self) -> dict[str, Any]: